Scope 3 Cat 7 Employee Commuting & Work-From-Home Calculator — DEFRA Per-Mode + Homeworking Factors
Compute Scope 3 Category 7 emissions for a hybrid workforce — commuting by DEFRA 2025 per-mode factors and homeworking by the DEFRA per-FTE-hour factor — in CO₂e on an AR5 GWP-100 basis.
Two streams, two units, one category. This calculator computes Scope 3 Category 7 — the emissions of your employees getting to work and of the days they work from home. Commuting is counted per kilometre on DEFRA’s per-mode factors; homeworking is counted per full-time-equivalent working hour on DEFRA’s homeworking factor. The two are different units because they measure different things — distance travelled versus time spent working at home — and the engine sums them into one Category 7 total.
You describe the commuting pattern; the work-from-home leg is what’s left of the week. Per cohort you enter headcount, mode, one-way distance, office-days per week, and whether the group is eligible to work from home. The engine derives the rest: round trips for the office days, and home-working hours for the remaining working days, using shared defaults of a five-day week, 7.5 home-working hours per day, and 44.4 working weeks per year. Shift one office day to home and that day’s emissions move automatically from the commute stream to the homeworking stream.
The factor basis is not like-for-like across modes. Car and motorbike factors are per vehicle-kilometre — occupancy-averaged and applied per employee — while bus and rail factors are per passenger-kilometre. A car factor and a train factor therefore answer slightly different questions, and a mode comparison should be read with that in mind rather than as a single ranked column.
Homeworking is DEFRA’s UK combined figure. The homeworking factor already blends home heating and office-equipment energy, so household heating must not be added a second time. The factor is published for the UK only; applied to a non-UK home-working population it is a documented proxy, not a country-specific value. Both streams are weighted on the IPCC AR5 GWP-100 basis, so there is a single CO₂e aggregate and no AR5-versus-AR6 choice to make.
Enter the one-way home-to-work distance per employee.
Audit mode exposes the full calculation chain + gas split.
Working-pattern assumptions (smart defaults — adjust if you know your figures)
These multiply every cohort. Office and WFH days both come out of the working week — a cohort working 3 office days of a 5-day week is modelled as commuting 3 days and (if WFH-eligible) home-working 2 days.
Add a line for each cohort of employees who share a commuting pattern (e.g. “London HQ — rail”, “Field engineers — diesel van”, “Fully remote”). Enter the headcount, mode, one-way distance, and office days per week. Work-from-home emissions are added automatically for the non-office days of WFH-eligible cohorts.
Roll up your whole workforce from a single CSV — one row per cohort. Parsing is fully client-side; your HR data never leaves your browser.
CSV schema (click to expand)
Required: headcount, mode, and distance (or distance_km). Optional: size, fuel, bus_type/rail_type (or reuse size for the type), office_days (default = working days/week), wfh (Y/N WFH-eligible, default Y), label.
mode accepts: car, motorbike, bus, rail, active (walk/cycle, zero). For car: size = small/medium/large/average and fuel = petrol/diesel/hybrid/bev/phev. For motorbike: size. For bus: coach/local_london/local_non_london/local_average. For rail: national_rail/london_underground/light_rail_tram/international_rail. Unknown combinations are skipped with a row note. distance is one-way and uses the unit toggle above; distance_km is always kilometres.
Drop a CSV file here or .
Or paste CSV text below.
Hold your workforce fixed and sweep the office-days-per-week policy from fully remote to fully in-office. Each step trades commuting against work-from-home — the RTO carbon curve shows whether more office days raise or lower your total Category 7, and where the minimum sits. Build your cohorts in the Workforce tab first.
WFH-eligible cohorts only. Non-eligible cohorts (e.g. field staff) hold their entered office days across the sweep.
Enter a distance of zero or more.
Add a cohort above to calculate
Results appear instantly. Commuting-vs-work-from-home split, per-cohort breakdown, per-FTE intensity, a hybrid-policy “RTO carbon curve”, and a full audit trail with DEFRA cell references all available after calculation.
Results are indicative, intended for screening and order-of-magnitude estimates. Factors are UK DEFRA 2026 (AR5 GWP-100): commuting travel on a distance-based method (per kilometre) and work-from-home on the DEFRA homeworking factor (per FTE working hour, office equipment + heating, UK-average). They are not valid for non-UK workforces — the homeworking factor in particular is UK-only and applied as a proxy to all work-from-home hours. Car and motorbike commuting factors are per vehicle-kilometre (occupancy-averaged); bus and rail are per passenger-kilometre. Battery-electric and plug-in-hybrid commuting uses the DEFRA UK-grid use-phase figure. For CDP, SECR, CSRD, or other regulatory submissions, validate factors against the primary DEFRA dataset, confirm commuting patterns against an employee survey or sampling, document your Scope 3 Category 7 inventory boundary, and report commuting and home-working consistently with your chosen base year. Business travel (reimbursed trips) is Scope 3 Category 6, not Category 7.
A finance team of a hundred splits its week three days in the office, two at home. Nobody on that team owns a company car or a company desk, yet every commute they drive and every radiator they run on a Tuesday at home is the company’s emission to report.
And for some of them, sending them into the office more often would lower the company’s footprint, not raise it.
Category 7 is commuting plus homeworking: commuting in kg CO₂e per kilometre by mode, homeworking at about 0.334 kg CO₂e per home-working hour. Counted per employee, on an AR5 basis. A day at home is a day not commuting.
What the Commuting + WFH calculator covers
This calculator computes Scope 3 Category 7: the emissions of your employees commuting to their regular place of work, and the emissions of the days they work from home instead. You describe each workforce cohort — how many people, how they travel, how far, and how often they are in the office — and the engine derives both the commuting and the homeworking emissions and sums them into a Category 7 total.
Why commuting and homeworking are the employer’s emissions
The employee owns the car, pays the rail fare, and heats their own home. So why does the footprint land on the employer’s inventory? Because Category 7 captures the emissions of employees travelling between home and work, and of employees working from home, in vehicles and buildings not owned or controlled by the company. The employee’s car is not the company’s Scope 1, and the employee’s home electricity is not the company’s Scope 2 — the company has no operational control over either. But the GHG Protocol still attributes those emissions to the employer as Category 7, because the travel and the home-working happen in service of the employer’s operations.
Employee commuting and work-from-home are Scope 3 Category 7 for the employer, not the employer’s Scope 1 or 2. The company owns neither the vehicle nor the home, so there is no direct-emission or purchased-energy component on its books — the whole of both streams sits in Category 7 as a value-chain emission.
The two streams
Category 7 has two parts, and this calculator computes both. The first is commuting: the round trips employees make between home and their workplace, by car, motorbike, bus, rail, or active travel. The second is homeworking: the energy an employee’s home draws — heating and office equipment — while they work there instead of commuting in. A hybrid workforce generates both, and the split between them is set by how the week divides between office and home.
What’s in, what’s a separate calculator
| Covered in this calculator | Out of scope — separate calculator or category |
|---|---|
| Commuting between home and the regular workplace, by DEFRA mode, per employee | Business travel — flights, hotels, and trips beyond the regular commute — is Scope 3 Category 6, each with its own calculator |
| Work-from-home energy — heating and office equipment — per home-working hour, on the DEFRA combined factor | The company’s own offices and their energy — that is the company’s Scope 1 and 2, not Category 7 |
| The hybrid split between office days and home days, derived from the working week | Employee air travel to another site or conference — Category 6 business travel, on the air calculator |
| Round trips — the engine doubles the one-way distance for the commute | Company-provided shuttle buses the firm operates or contracts — these may sit in Scope 1 or Category 6, not commuting |
Two streams — commuting per kilometre, homeworking per hour
This is the page’s signature methodological point. Category 7 is not one factor applied to one activity figure — it is two streams measured in two different units, reconciled into a single total.
Commuting — distance, by mode
The commuting stream is per kilometre. Each mode carries its own DEFRA 2025 factor, and the engine multiplies the round-trip distance by the office-day count and the cohort headcount to get the annual commuting kilometres, then by the mode factor. A diesel car commute and a rail commute over the same distance produce very different numbers, because the factors differ by an order of magnitude. The one subtlety is the basis: car and motorbike factors are per vehicle-kilometre, occupancy-averaged and applied to each employee, while bus and rail factors are per passenger-kilometre. They are not strictly like-for-like, so a mode comparison is a guide to magnitude rather than a single clean ranking.
Homeworking — time, not distance
The homeworking stream is per working hour, not per kilometre — because a home-working day has no journey to measure. DEFRA publishes a single combined homeworking factor of 0.33378 kg CO₂e per full-time-equivalent working hour, blending the home’s heating and office-equipment energy attributable to the working day. The engine multiplies that factor by the home-working hours a cohort generates: the days not spent in the office, times the home-working hours per day, times the working weeks, times the headcount. Crucially, the combined factor already includes heating — so household heating must never be added again as a separate line.
The DEFRA homeworking factor of 0.33378 kg CO₂e per hour already blends home heating and office-equipment energy. Do not add a separate household-heating figure on top — that double-counts the largest part of the homeworking footprint. The combined factor is the whole home-working emission per working hour, not just the equipment.
Reconciling the two into one total
Because the streams are summed, the Category 7 total is the commuting kilometres at their mode factors plus the home-working hours at the homeworking factor. The structure looks like this:
Category 7 (kg) = Σ (commuting-kmcohort × mode factor) + Σ (home-working FTE-hourscohort × 0.33378)
Commuting is per kilometre by mode; homeworking is per home-working hour. A day at home is a day not commuting — the two streams trade off across the week.
The chart below shows that trade-off for a single cohort: a national-rail group splitting its week three days in the office and two at home. Even though the rail commute covers a real distance every office day, the homeworking stream is the larger of the two — because home heating, charged across every home-working hour, adds up faster than a short low-carbon rail trip.
Category 7 split for a 100-FTE national-rail cohort, 18 km one-way, 3 office days per week, AR5 GWP-100. Bars scaled to the combined total (39.23 tCO₂e). For a short, low-carbon rail commute the homeworking stream is the larger share. DEFRA 2025 via MasterBrain v2026.110.
The hybrid week — work-from-home is what’s left of it
The thing that makes Category 7 awkward for a hybrid workforce is that the two streams are coupled. You do not enter commuting and homeworking separately — you enter the commuting pattern, and the homeworking falls out of the rest of the working week.
What you enter, and what the engine derives
Per cohort you give the engine five things: headcount, commuting mode, one-way distance, office-days per week, and whether the cohort is eligible to work from home. From there the engine derives both legs against shared defaults — a five-day working week, 7.5 home-working hours per day, and 44.4 working weeks per year. The office days drive the commute: distance, doubled for the round trip, times office days, times weeks, times headcount, times the mode factor. The remaining working days drive the homeworking: five minus the office days, times 7.5 hours, times weeks, times headcount, times the homeworking factor.
Work-from-home is derived, not entered. Office-days per week sets the commute; the rest of the five-day week becomes home-working days for any cohort flagged WFH-eligible. Move one day from office to home and the engine moves that day’s emission from the commuting stream to the homeworking stream automatically — you never enter home hours by hand.
Why the coupling matters — and where double-counting creeps in
Because a day is either an office day or a home day, the two streams cannot both claim it — which is exactly what protects the total from double-counting, provided the office-day count is right. The common error is to count a full commute for every working day and a full week of homeworking, as if employees did both every day. They do not: a three-day-office cohort commutes three days and works from home two, not five and five. Getting the office-day split right per cohort is the single most important input, because it allocates every working day to one stream or the other exactly once.
Do not count a full commute for every working day and a full week of homeworking on top. A hybrid week splits into office days and home days that sum to the working week — not double it. A cohort in the office three days a week commutes three days and works from home two; counting five of each inflates Category 7 by roughly the headcount again.
The return-to-office paradox — when more office days cut emissions
Here is the finding that makes the calculator worth running rather than estimating. Because commuting and homeworking trade off across the week, sending people into the office more often does not always raise Category 7 — for some cohorts it lowers it. Whether it does depends entirely on the commute.
The rail cohort — more office days, lower emissions
Take the national-rail cohort: 100 people, 18 km each way, on a low-carbon per-passenger-kilometre factor. Run it across the return-to-office curve and the total falls as office days rise — from 55.57 tonnes at fully remote, to 39.23 at three office days, to 28.34 at five. The reason is the homeworking factor. Every home-working hour carries 0.33378 kg of mostly home-heating carbon, and a full home day of 7.5 hours costs more than a short, clean rail round trip. For this cohort, a home day is the higher-carbon choice.
National-rail cohort (100 FTE, 18 km one-way), Category 7 total across the return-to-office curve, AR5 GWP-100. Bars scaled to the fully-remote total. More office days lower the total — the rail commute is cheaper than the home-heating it displaces. DEFRA 2025 via MasterBrain v2026.110.
The car cohort — the curve runs the other way
Now swap the mode. A diesel-car cohort — 100 people, 20 km each way, on a per-vehicle-kilometre factor an order of magnitude above rail — runs the opposite way: 55.57 tonnes fully remote, 114.43 at three office days, 153.66 at five. Here every office day adds a high-carbon car round trip that dwarfs the home day it replaces, so the total rises with office attendance. Same workforce size, same home-working factor, opposite conclusion — set entirely by the commute mode.
Diesel-car cohort (100 FTE, 20 km one-way), Category 7 total across the same return-to-office curve, AR5 GWP-100. Bars scaled to the fully-in-office total. More office days raise the total — the car commute outweighs the home-heating it displaces. The two curves cross at fully remote, where both cohorts are pure homeworking. DEFRA 2025 via MasterBrain v2026.110.
Office attendance is not uniformly good or bad for Category 7 — it depends on the commute. A low-carbon rail or active commute makes a home day the higher-carbon option, so more office days cut the total; a car commute makes the office day the higher-carbon option, so more office days raise it. A blanket return-to-office or work-from-home policy has opposite emission effects on a rail cohort and a car cohort, which is why modelling beats assuming.
Segment your workforce by commute mode before reading a return-to-office decision as a carbon win or loss. The lever that genuinely lowers Category 7 for car cohorts is mode shift — to rail, to active travel, to a cleaner vehicle — not attendance policy alone. Model your real cohorts across the office-day range to see which way each one’s curve runs before setting a single firm-wide rule.
How the calculation works — cohorts to CO₂e
Every cohort runs the same two-stream calculation: office days drive the commute, the rest of the week drives the homeworking, and the two sum. What changes between cohorts is the mode and the office-day split.
Fully in-office
Five office days, no home days. The cohort is pure commuting — homeworking is zero. The number is driven entirely by mode and distance. The trap: forgetting to double the one-way distance for the round trip.
Hybrid
The common case: some office days, some home days. Both streams fire, and the office-day split sets the balance. The trap: counting a full commute and a full week of homeworking instead of splitting the week.
Fully remote
No office days, all home days. The cohort is pure homeworking on the 0.33378 factor; commuting is zero. The trap: assuming remote means zero Category 7 — home heating is a real, often substantial, line.
Mixed cohorts
Different teams on different modes and patterns, summed. Enter each as its own cohort. The trap: averaging the whole workforce to one mode and one office-day count, which hides the rail-versus-car reversal.
The defaults, and where to override them
The engine applies shared assumptions so you enter only what varies between cohorts: a five-day working week, 7.5 home-working hours per day, and 44.4 working weeks per year — the latter already netting out leave and public holidays. These drive both legs, so they should reflect your actual working pattern; a workforce on a four-day week or a different leave allowance needs the defaults adjusted before the totals are defensible. Everything else — headcount, mode, distance, office days, and work-from-home eligibility — is entered per cohort, which is what lets the calculator surface the mode-by-mode differences a single workforce average would bury.
Build cohorts around commute mode and location, not job title. A rail-commuting head-office cohort and a car-commuting regional cohort behave oppositely across the office-day range, so splitting them lets you see — and act on — the difference. Lumping them into one average mode erases exactly the signal the calculator exists to show.
Worked example — a national-rail hybrid cohort
This example runs one cohort end to end: 100 employees commuting by national rail, 18 km each way, three days in the office and two at home, on the engine’s default working pattern. It shows both streams and how they sum.
The commuting leg
Three office days a week, doubled for the round trip, across 44.4 working weeks, for 100 people, at 18 km each way, gives the annual commuting distance; the national-rail factor converts it to CO₂e.
| Step | Calculation | Result |
|---|---|---|
| Annual commuting kilometres | 18 km × 2 × 3 days × 44.4 weeks × 100 people | 479,520 km |
| Apply national-rail factor | 479,520 km × 0.03546 kg CO₂e/km | 17,003.8 kg |
| Commuting leg | — | 17.00 tCO₂e |
The homeworking leg
The two days a week not in the office become home-working days: 7.5 hours each, across the same 44.4 weeks, for 100 people, at the DEFRA combined homeworking factor.
| Step | Calculation | Result |
|---|---|---|
| Annual home-working hours | (5 − 3) days × 7.5 h × 44.4 weeks × 100 people | 66,600 FTE-hours |
| Apply homeworking factor | 66,600 h × 0.33378 kg CO₂e/h | 22,229.7 kg |
| Homeworking leg | — | 22.23 tCO₂e |
DEFRA 2025 factors, AR5 GWP-100. National rail 0.03546 kg CO₂e per passenger-km; homeworking combined 0.33378 kg CO₂e per FTE working hour. Defaults: 5-day week, 7.5 WFH hours/day, 44.4 working weeks/year. DEFRA 2025 via MasterBrain v2026.110.
The headline is the split: for this cohort the larger share of Category 7 is the home days, not the commute. That is the counter-intuitive result the return-to-office section builds on — and it only shows up because the calculator measures both streams rather than treating commuting as the whole of Category 7.
Commuting modes and homeworking — the factors
The tables below set out the DEFRA 2025 factors behind both streams. Read the commuting table with the basis caveat in mind: car and motorbike are per vehicle-kilometre, bus and rail are per passenger-kilometre, so the column is a guide to magnitude rather than a strict like-for-like ranking.
Commuting — by mode
| Mode | Factor (kg CO₂e/km) | Basis |
|---|---|---|
| Diesel car (average) | 0.17304 | per vehicle-km |
| Petrol car (average) | 0.16272 | per vehicle-km |
| Hybrid car (average) | 0.12825 | per vehicle-km |
| Motorbike (average) | 0.11367 | per vehicle-km |
| Local bus (average) | 0.10385 | per passenger-km |
| Battery-electric car (average) | 0.03663 | per vehicle-km, UK grid use-phase |
| National rail | 0.03546 | per passenger-km |
| Light rail / tram | 0.02860 | per passenger-km |
| London Underground | 0.02780 | per passenger-km |
| Coach | 0.02776 | per passenger-km |
| International rail | 0.00446 | per passenger-km |
| Active travel (walk / cycle) | 0 | zero-emission, explicit line |
DEFRA 2025 commuting factors, AR5 GWP-100, scope 3 Category 7. Car, motorbike, and battery-electric factors are per vehicle-kilometre (occupancy-averaged, applied per employee); bus and rail factors are per passenger-kilometre — the two bases are not directly comparable. Battery-electric is the UK-grid use-phase figure. DEFRA 2025 via MasterBrain v2026.110.
The spread across modes is roughly forty-fold — from a diesel car at 0.17304 kg per kilometre to international rail at 0.00446 — but the per-vehicle versus per-passenger basis means the car and rail ends of the table are not a clean apples-to-apples ranking. Mode shift from a car to rail or active travel is nonetheless the largest single lever a company has over the commuting stream.
Homeworking — the combined factor and its parts
DEFRA’s homeworking factor is published as three figures: office equipment, heating, and the combined total the engine uses. The split shows why heating dominates — it is roughly ten times the office-equipment component.
DEFRA 2025 homeworking factors, kg CO₂e per FTE working hour, AR5 GWP-100, UK only. Bars scaled to the combined factor. Heating is roughly ten times the office-equipment component — it is the dominant part of the home-working footprint. The engine applies the combined figure; heating is already included. DEFRA 2025 via MasterBrain v2026.110.
Home heating, not laptops and screens, is the bulk of the homeworking factor — 0.30234 of the 0.33378 combined figure. That is why a full home day can outweigh a short low-carbon commute, and why the engine uses the combined factor: applying office-equipment alone would understate the home-working stream by an order of magnitude.
Data quality and the activity-data hierarchy
Because the factors are fixed and published, data quality on a Category 7 inventory is almost entirely about the activity data: how accurately you know each cohort’s mode, distance, and office-day split, and whether those come from a survey or from an assumption. The reporting expectation is to use the most specific commuting and attendance data available, and to be explicit about where defaults stand in for measured inputs.
| Tier | Commuting and attendance data | Typical source |
|---|---|---|
| Primary / survey-based | Actual mode, distance, and office-day pattern per employee or cohort, from a commuting survey, plus measured attendance from access or booking systems | Employee commuting survey, desk-booking or badge-in data, HR working-pattern records |
| Modelled cohort | Cohort mode and distance from postcode-to-site routing, office-day split from policy, on the engine defaults | HR location data, travel-plan assumptions, hybrid-working policy |
| Default / proxy | Whole-workforce average mode and distance, a single assumed office-day split, UK homeworking factor applied to all home hours including non-UK | Headcount with national-average commuting assumptions |
The highest-value improvement for most Category 7 inventories is a commuting survey that resolves mode and distance per cohort, because mode is what drives the per-kilometre factor and sets which way a cohort’s return-to-office curve runs. The second is accurate attendance data for the office-day split, since that allocates each working day to the commuting or homeworking stream. The honest disclosure names which cohorts rest on survey data and which on assumptions, and flags where the UK homeworking factor has been applied as a proxy to a non-UK home-working population.
Audit checklist — what gets flagged in Cat 7 assurance
Employee commuting and homeworking is an assumption-heavy Category 7 line, and the same findings recur. Each traces to a stream-allocation error, a unit error, or an activity-data gap rather than to the arithmetic.
01 — Commute and homeworking double-counted
Counting a full week of commuting and a full week of homeworking for a hybrid cohort. The week splits into office days and home days that sum to the working week — not double it. Allocate each working day to one stream once.
02 — Remote treated as zero Category 7
Assuming a fully-remote cohort has no commuting footprint and stopping there. Homeworking is a real line — home heating at 0.33378 per hour is often substantial. A remote workforce still reports Category 7.
03 — One-way distance not doubled
Applying the mode factor to the one-way commute. A commute is a round trip — the engine doubles the one-way distance. Halving the commute halves the whole commuting stream.
04 — Household heating added twice
Adding a separate home-heating estimate on top of the combined homeworking factor. The 0.33378 figure already includes heating. Adding it again double-counts the largest part of the homeworking stream.
05 — Whole workforce on one average mode
Collapsing every employee to a single average mode and office-day split. This hides the rail-versus-car reversal and produces a number no cohort actually generates. Build cohorts by mode and location.
06 — UK homeworking factor on a global workforce
Applying the UK-only homeworking factor to non-UK home workers without flagging it. No non-UK DEFRA homeworking factor exists; using the UK one is a documented proxy that belongs in the disclosure, not a silent substitution.
Reporting context — Scope 3, IFRS S2, CSRD E1, SECR
Category 7 emissions feed the same disclosure regimes as the rest of the Scope 3 inventory. The common thread across the frameworks below is that all of them want the activity basis and the factor source disclosed — which is why keeping the office-day split clean and the survey-versus-assumption distinction transparent matters beyond the number itself.
| Framework | Role for Category 7 emissions | Disclosure cadence |
|---|---|---|
| GHG Protocol Scope 3 Standard | The accounting standard. Defines Category 7 employee commuting, including teleworking, and the activity-based method this calculator uses. | Same as the company’s reporting cycle |
| UK DEFRA Conversion Factors | The factor source — per-mode commuting factors and the homeworking factor, on the AR5 GWP-100 basis, refreshed annually. | Annual refresh (each DEFRA release) |
| IFRS S2 (ISSB) | The global disclosure baseline. Requires Scope 3 disclosure including employee commuting where material, with the calculation methodology disclosed. | Annual, aligned with financial statements |
| CSRD ESRS E1 (EU) | The EU climate standard. ESRS E1 carries Scope 3 employee-commuting emissions in CO₂e as part of the gross Scope 3 total. | Annual sustainability statement |
| UK SECR | UK Streamlined Energy and Carbon Reporting. Employee commuting is within voluntary Scope 3 scope; many reporters include it as part of a complete workforce footprint. | Annual, with the directors’ report |
For the reporting mechanics, the paired employee commuting and work-from-home methodology sets out the two-stream method, the per-mode and homeworking factors, and the hybrid-week apportionment in full. Alongside it, the business travel car methodology and the hotel stay HCMI methodology cover the Category 6 business-travel lines that sit next to commuting in a complete travel inventory.
Data sources, factors, and GWP basis
The factors — sources and structure
Both streams draw on the DEFRA 2025 UK Government greenhouse gas conversion factors. The commuting stream uses DEFRA’s per-mode passenger and vehicle factors — car by fuel, motorbike, bus, and rail — expressed in kg CO₂e per kilometre, with the per-vehicle versus per-passenger basis varying by mode. The homeworking stream uses DEFRA’s homeworking factor, expressed in kg CO₂e per full-time-equivalent working hour, as a single combined figure blending home heating and office-equipment energy. The full DEFRA tables sit in the DEFRA emission factors reference, and the travel-related factors in the business travel and freight logistics factors reference.
GWP basis
Both streams are weighted on the IPCC AR5 GWP-100 basis, the DEFRA convention for its published factors, and both report a single CO₂e aggregate with no per-gas split — so there is no AR5-versus-AR6 reweighting available and no toggle. For background on how the assessment-report bases differ, see the global warming potential definition. Because commuting and homeworking share the same basis, the Category 7 total is internally consistent without any reconciliation between the two streams.
Coverage limit — UK homeworking only
One coverage limit is worth naming plainly: DEFRA publishes a homeworking factor for the UK only. There is no country-specific homeworking factor for other markets, so a non-UK home-working population is computed on the UK figure as a documented proxy. For a predominantly UK workforce this is a close fit; for a global one it is an approximation that the disclosure should state. The commuting factors carry the usual DEFRA mode coverage and are applied per cohort as entered.
Versioning and update cadence
DEFRA refreshes its conversion factors annually, so both streams update on that cadence; the MasterBrain version against which a result was computed is stamped on the output, so a figure computed against one vintage and the same figure recomputed against a later one are distinguishable in restatement work. The employee commuting and work-from-home methodology documents the two-stream method and the factor sources in full.
What’s next — completing your travel and commuting inventory
Commuting and homeworking is the Category 7 line. A complete workforce-and-travel picture adds the Category 6 business-travel legs — air, rail, road, and hotel — that cover trips beyond the daily commute. The calculators below cover the rest of the surface.
✓ Live
Employee Commuting + WFH
Commuting by DEFRA mode and homeworking per FTE-hour, across the hybrid week. The calculator on this page.
✓ Live
Business Travel Car
Grey-fleet, hire car, taxi, and motorbike on DEFRA per-kilometre factors — the business-travel road leg.
✓ Live
Business Travel Rail
National, international, tram, and Underground, metered per passenger-kilometre.
✓ Live
Hotel Stay
Room-nights by country or property class, for the accommodation leg of business travel.
✓ Live
GHG Inventory Aggregator
Roll Category 7 together with every other Scope 1, 2 and 3 source into one auditable corporate carbon footprint — the organisation-level inventory this category feeds into.
For the full methodological treatment — the two-stream method, the per-mode and homeworking factors, and the hybrid-week apportionment — see the employee commuting and work-from-home methodology. For the adjacent business-travel boundaries, the Business Travel Air calculator covers flights with their radiative-forcing treatment, and the Scope 1 Mobile Combustion calculator is the right home for company-owned vehicles, which are the firm’s direct emissions rather than Category 7. Where the question is whether a vehicle or asset is the company’s to report at all, the operational control definition sets the boundary.
Frequently asked questions
It is the company’s Scope 3 Category 7. The employee owns the car and pays for the fuel, so it is not the company’s Scope 1 or 2 — the company has no operational control over the vehicle. But the GHG Protocol attributes commuting and work-from-home emissions to the employer as a value-chain emission, because the travel and home-working happen in service of the employer’s operations.
Split the working week between office days and home days — they sum to the week, not double it. A cohort in the office three days a week commutes three days and works from home two. The calculator does this automatically: you enter office-days per week, and it derives the home days from the rest of the week. The common error is counting a full week of commuting and a full week of homeworking on top of each other.
For some cohorts, yes. A home-working day carries about 0.334 kg CO₂e per hour, mostly home heating — so a full home day can outweigh a short, low-carbon commute. For a national-rail or active-travel cohort, more office days lower Category 7. For a car-commuting cohort the opposite holds: every office day adds a high-carbon round trip, so more office days raise the total. The direction depends entirely on the commute mode.
DEFRA’s combined homeworking factor is 0.33378 kg CO₂e per full-time-equivalent working hour, which blends home heating (0.30234) and office equipment (0.03144). The calculator uses the combined figure, so heating is already included — you should not add a separate household-heating estimate. The factor is published for the UK only.
They are on different bases. Car and motorbike factors are per vehicle-kilometre — occupancy-averaged and applied per employee — while bus and rail factors are per passenger-kilometre. So a car factor and a train factor measure slightly different things, and a mode table is a guide to magnitude rather than a strict like-for-like ranking. The forty-fold spread from diesel car to international rail is still real, but read it with the basis in mind.
No. A fully remote cohort has no commuting, but its homeworking stream is real and often substantial — home heating and office equipment at 0.33378 kg CO₂e per working hour. Treating remote as zero Category 7 is a common error; a remote workforce still reports a homeworking footprint.
No. You enter the commuting pattern per cohort — headcount, mode, one-way distance, office-days per week, and work-from-home eligibility — and the engine derives the homeworking from the rest of the working week. Move one office day to home and that day’s emission shifts automatically from the commuting stream to the homeworking stream. You never enter home-working hours by hand.
Partly. The commuting factors are DEFRA mode factors applied as entered. The homeworking factor, though, is published for the UK only — there is no country-specific DEFRA homeworking factor for other markets — so a non-UK home-working population is computed on the UK figure as a documented proxy. For a UK workforce this is a close fit; for a global one the disclosure should state that the homeworking leg uses a UK proxy.
You enter the one-way distance and the engine doubles it for the round trip. So an 18 km one-way commute is counted as 36 km per office day. Applying a mode factor to the one-way distance without doubling halves the commuting stream — a recurring error the round-trip handling is designed to prevent.
AR5 GWP-100. DEFRA weights both the commuting and homeworking factors on AR5, the DEFRA convention, and both report a single CO₂e aggregate with no per-gas split — so there is nothing to reweight between AR5 and AR6 and no toggle. The two streams share the same basis, so the Category 7 total is internally consistent.
Methodology notes and limitations
Scope and boundary. This calculator covers employee commuting and work-from-home under GHG Protocol Scope 3 Category 7. The employee’s vehicle and home are not the company’s Scope 1 or 2 — the company has no operational control over them — but both streams are attributed to the employer as Category 7. Business travel beyond the regular commute is Category 6, and the company’s own offices are its Scope 1 and 2, not Category 7.
Two streams, two units. Commuting is computed per kilometre on DEFRA per-mode factors; homeworking is computed per full-time-equivalent working hour on the DEFRA combined homeworking factor. The two are summed into one Category 7 total. They are different units because they measure different activities — distance travelled versus time spent working at home.
The hybrid week is derived, not entered. The user enters headcount, mode, one-way distance, office-days per week, and work-from-home eligibility per cohort; the engine derives both legs against shared defaults of a five-day week, 7.5 home-working hours per day, and 44.4 working weeks per year. Office days drive the commute; the remaining working days drive the homeworking. A workforce on a different working pattern should have the defaults adjusted before the totals are relied on.
The commute is a round trip. The engine doubles the one-way distance entered. Active travel — walking and cycling — is carried as an explicit zero-emission line rather than omitted, so a cohort’s mode mix is visible in full.
Factor basis is not like-for-like across modes. Car and motorbike factors are per vehicle-kilometre, occupancy-averaged and applied per employee; bus and rail factors are per passenger-kilometre. A mode comparison is a guide to magnitude, not a strict ranking, and this distinction should be stated where a car cohort and a rail cohort are compared.
Homeworking is the UK combined factor. The 0.33378 kg CO₂e per FTE working-hour figure already blends home heating and office equipment — household heating must not be added separately. The factor is published for the UK only; applied to a non-UK home-working population it is a documented proxy, not a country-specific value, and the disclosure should say so.
GWP basis. Both streams are on the IPCC AR5 GWP-100 basis with no per-gas split, so there is no AR5-versus-AR6 toggle and no reconciliation between the streams. The total is a single CO₂e aggregate.
Activity data carries the accuracy, and no assurance opinion is given. The factors are fixed published values, so the result’s accuracy depends on the mode, distance, and office-day split entered per cohort. The calculator takes those as entered and does not independently verify them; the user is responsible for the activity-data basis and for documenting the source of each cohort’s inputs. Results are estimates and do not constitute an assurance opinion. They should be reviewed by a qualified practitioner before use in IFRS S2 disclosures, CSRD ESRS E1 datapoints, UK SECR returns, or other regulatory submissions.