Scope 3 Cat 4 Sea Freight Calculator (Container / Bulk / Tanker / RoRo)
Compute well-to-wheel ocean-freight emissions under the GLEC Framework v3.2 — per tonne-km for bulk, tanker, RoRo, and general cargo, and per TEU-km for containerised cargo, with vessel-class and size-band intensities.
Two activity formulas — by cargo type:
Non-container (bulk, tanker, RoRo, general cargo):
Freight emissions (kg CO₂e) = Mass (tonnes) × Distance (km) × WTW intensity (kg CO₂e per tonne-km)
Containerised cargo:
Freight emissions (kg CO₂e) = TEU × Distance (km) × WTW intensity (kg CO₂e per TEU-km)
Sea freight is the only mode in the GLEC keyspace that carries two incompatible activity units. The 10 non-container vessel classes are priced per tonne-kilometre; containerised cargo is priced per twenty-foot-equivalent-unit-kilometre (TEU-km). The two never share a factor table, a worked example, or a sum. A container leg and a bulk leg in the same shipment are computed and reported as separate totals, because a TEU-km and a tonne-km are different physical quantities.
Vessel-class selection (non-container). The selection axis is vessel class × size band — there are no regional sets, unlike road freight. The 10 classes are bulk carrier, oil tanker, chemical tanker, general cargo, liquefied gas tanker, other-liquids tanker, RoPax ferry, refrigerated bulk, RoRo, and vehicle carrier. The size-band unit varies by class: deadweight tonnage (dwt) for bulk, tanker, cargo, RoRo, and refrigerated; cubic metres (cbm) for liquefied gas; gross tonnage (gt) for RoPax and vehicle carriers. Intensity falls steeply with vessel size — a small bulker under 10,000 dwt on HFO runs at 0.0312 kg CO₂e/tonne-km, a 60,000–100,000 dwt Panamax at 0.0052, roughly six times lower.
Trade-lane selection (container). Container intensity is keyed by trade lane (38 lanes including an industry average, the Panama trade, and the trans-Atlantic, trans-Pacific, and Suez corridors) and by dry or reefer. There is no vessel-size or fuel segment on container rows — the trade-lane average already embeds the typical vessel mix on that route. Where the specific lane is unknown, the industry-average row (dry 0.0717, reefer 0.1423 kg CO₂e/TEU-km) is the defensible default.
WTW headline; WTT/TTW split. The calculator computes the well-to-wheel total — the full fuel lifecycle from extraction to combustion. GLEC publishes the well-to-tank (upstream fuel production) and tank-to-wheel (combustion) components alongside each row; these are reported in worked examples as fixed component pairs and do not vary with user inputs. For a small bulker the WTW of 0.0312 decomposes as 0.0047 WTT + 0.0265 TTW.
Distance adjustment factor (DAF). Great-circle port-to-port distance understates the actual sailed distance because ships route around landmasses, through canals, and along shipping lanes. GLEC publishes a distance-adjusted value (with a roughly 15% uplift) for out-of-route sailing. The calculator applies the great-circle distance you enter at face value; where you need the distance-adjusted basis, apply the DAF uplift to the distance before entry, or use the actual sailed distance from the carrier.
Marine fuels. Non-container rows carry three fuel options — heavy fuel oil (HFO), very-low-sulphur fuel oil (VLSFO), and marine diesel oil (MDO). VLSFO became the default marine fuel after the IMO 2020 sulphur cap. Container rows carry no fuel segment; the trade-lane average reflects the prevailing fuel mix on the route.
Category boundary. This calculator covers upstream transport and distribution (GHG Protocol Scope 3 Category 4) by sea. The same GLEC sea factors apply to downstream distribution under Category 9 — identical arithmetic, different category line. Road, air, rail, inland-waterway, and cold-chain freight use their own factor sets and are out of scope here.
All factors: GLEC Framework v3.2 (ISO 14083), well-to-wake, AR6 GWP-100.
Add each ocean-freight leg. Choose the vessel family, then refine the vessel class, size band and fuel (or, for containers, the trade lane and dry/reefer). Container legs are priced per TEU-km; all other vessels per tonne-km — the two are never combined.
Enter a routed (actual) sea distance for audit-grade output; the estimate option is approximate and lowers the leg’s data-quality score.
Compare two shipment configurations side-by-side — e.g. container trans-Pacific vs bulk carrier for the same cargo, small tanker vs VLCC, or HFO vs VLSFO. The result shows the delta plus what drove it (vessel/route intensity, payload, distance).
Option A
Option B
Add a shipment leg above and click Calculate
Results appear after calculation: well-to-wake total, the well-to-tank / tank-to-wake split, per-leg contribution, an auto-derived data-quality score, full audit trail, and JSON / CSV export.
Results are indicative, intended for Scope 3 Category 4 sea-freight screening. Emission factors are GLEC Framework v3.2 (ISO 14083-aligned) well-to-wake intensities and represent average-laden vessel operation; they exclude empty-leg (ballast) repositioning beyond the GLEC average and do not include port handling, drayage, warehousing or inland legs. For regulatory disclosure (CSRD/ESRS E1, SECR, CDP, SBTi), prefer primary carrier data (Clean Cargo / CCWG or vessel-specific fuel logs) where available, validate routed distances, and report the well-to-tank (WTT) share within Category 4 rather than as a separate inventory line. Container intensities are per TEU-km and non-container per tonne-km — the two activity bases are not interchangeable.
Sea freight moves roughly four-fifths of world trade by volume and is the lowest-carbon way to shift cargo across an ocean — yet it is the freight mode where carbon accounting most often goes wrong, because it is the one mode that carries two incompatible activity units. Bulk, tanker, and RoRo cargo is priced per tonne-kilometre; containerised cargo is priced per TEU-kilometre. Sum the two and the number is meaningless.
This calculator applies GLEC Framework v3.2 intensities by vessel class, size band, and trade lane — keeping the two units rigorously separate, the way an assurer expects.
Sea-freight emissions equal cargo mass (tonnes) × distance × the GLEC tonne-km intensity for bulk, tanker, and RoRo cargo — or TEU × distance × the TEU-km intensity for containers. The two units are never summed. A Panamax bulker runs at 0.0052 kg CO₂e per tonne-km.
What sea freight covers in Scope 3 Category 4
GHG Protocol Scope 3 Category 4 — upstream transportation and distribution — covers the movement of purchased goods between a company’s tier-1 suppliers and its own operations, plus third-party logistics the reporting company pays for. Sea freight is the dominant mode by tonnage for any organisation with an international supply chain: the bulk carriers, tankers, container ships, and RoRo vessels that move raw materials and finished goods between continents.
Category 4 vs Category 9 — same factors, different direction
The line between Category 4 and Category 9 is the direction of the goods flow, not the arithmetic. Category 4 is upstream — transport the reporting company pays for, bringing goods in. Category 9 is downstream — transport of sold products after they leave the company’s control. The GLEC sea intensities are identical across both; the only difference is which Scope 3 category line the result is booked to. A shipping line reporting its own vessel emissions books them to Scope 1; a shipper paying that line books the same tonne-km or TEU-km to Scope 3 Category 4.
Mode boundary — what’s in, what’s elsewhere
| Covered in this calculator | Out of scope — separate freight mode |
|---|---|
| Bulk carriers, oil and chemical tankers, general cargo, liquefied-gas and other-liquids tankers — per tonne-km | Road freight — heavy goods vehicles by region, class, load, and fuel: see the Road Freight Calculator |
| Containerised cargo by trade lane, dry or reefer — per TEU-km | Air freight — bellyhold and freighter jet-fuel intensities (separate calculator, in development) |
| RoRo and vehicle carriers, RoPax ferries — per tonne-km on a gross-tonnage size band | Rail freight — diesel and electric traction by commodity profile (separate calculator, in development) |
| Refrigerated bulk (reefer) vessels — per tonne-km across deadweight bands | Inland waterway — barge convoys and motor vessels on rivers and canals (separate factor set, in development) |
| The ocean leg of an intermodal journey | Cold-chain logistics — reefer transport adds refrigerant-leakage and reefer-energy components (separate calculator, in development) |
Sea freight is the lowest-carbon mode per unit of cargo moved over distance — a large bulker runs more than an order of magnitude below road haulage per tonne-km. But “low intensity” and “low total” are not the same: ocean distances are so long that the absolute footprint of an intercontinental shipment can still be substantial. The intensity is low; the tonne-km count is high.
The two-unit problem — tonne-km vs TEU-km
This is the single most important thing to get right on a sea-freight inventory, and the error an assurer looks for first. GLEC prices the 10 non-container vessel classes per tonne-kilometre and containerised cargo per TEU-kilometre, and the two are different physical quantities that cannot be added.
| Dimension | Non-container classes | Containerised cargo |
|---|---|---|
| Activity unit | Tonne-kilometre (mass × distance) | TEU-kilometre (containers × distance) |
| Key shape | sea.<class>.<size_band>.<fuel> |
sea.container.<trade_lane>.<dry|reefer> |
| Selection axis | Vessel class × size band × marine fuel | Trade lane × dry/reefer (no size, no fuel) |
| Size band unit | dwt (bulk/tanker/cargo/RoRo/reefer), cbm (gas), gt (RoPax/vehicle carrier) | None — embedded in the lane average |
| Industry-average default | No single cross-class aggregate; pick the class and band | Yes — industry_average (dry 0.0717, reefer 0.1423 kg CO₂e/TEU-km) |
When to use which
The choice follows the cargo, not the vessel. If the cargo is loose, poured, pumped, or rolled — ore, grain, crude, chemicals, vehicles — it is priced per tonne-km against the appropriate vessel class. If the cargo moves in shipping containers, it is priced per TEU-km against the trade lane, regardless of what is inside the boxes. A single container ship carries the cargo of hundreds of shippers; the TEU-km basis attributes the vessel’s emissions per container-slot-kilometre, which is the only tractable allocation for containerised trade.
Never sum a tonne-km total and a TEU-km total into one figure, and never set a reefer-bulk tonne-km intensity (0.0436 kg CO₂e/tonne-km for the largest refrigerated-bulk band on VLSFO) beside a container reefer TEU-km intensity (0.1423 kg CO₂e/TEU-km) as a like-for-like comparison. They look comparable — both are “reefer” emissions — but one is per tonne and one is per container. A mixed shipment with both bulk and container legs is reported as two separate totals on two separate units. Merging them is the most common sea-freight audit finding.
Both units roll up into the same absolute kg CO₂e total once each leg’s emissions are computed — kilograms of CO₂e are kilograms regardless of the activity denominator. What must never be merged is the activity figures (the tonne-km and the TEU-km) or the intensities. The emissions outputs sum; the activity inputs and the per-unit intensities do not.
How the calculation works — activity × WTW intensity
Each leg reduces to one multiplication, run per leg and summed into the absolute emissions total at the end:
Non-container: kg CO₂e = Mass (tonnes) × Distance (km) × WTW intensity (kg CO₂e per tonne-km)
Container: kg CO₂e = TEU × Distance (km) × WTW intensity (kg CO₂e per TEU-km)
The activity spine
For non-container cargo, the activity is mass in tonnes multiplied by the port-to-port distance in kilometres. For containers, it is the number of TEU multiplied by distance. A 40-foot container is two TEU; a 20-foot container is one. Distance for sea freight is the over-water routing distance between ports — see the DAF section below for the great-circle-versus-sailed-distance distinction that materially affects the result.
Well-to-wheel, well-to-tank, tank-to-wheel
Well-to-tank (WTT)
The upstream emissions of extracting, refining, and delivering the marine fuel before it reaches the vessel’s bunkers. See the well-to-tank definition for the accounting boundary.
Tank-to-wheel (TTW)
The combustion emissions at the vessel — the CO₂e released by burning the bunker fuel under way. For a small bulker on HFO this is roughly 85% of the well-to-wheel total.
Why WTW is the headline
Scope 3 Category 4 requires the full upstream-and-combustion footprint of the transport service. The WTW total is the figure that feeds the inventory; reporting TTW alone understates the footprint by the upstream fuel-production share.
Vessel class and size band — no regions
Unlike road freight, the sea set has no regional dimension — a bulk carrier’s intensity depends on its class and deadweight, not on where it sails. Select the vessel class that carried the cargo and the size band that matches the vessel’s deadweight (or gross tonnage / cubic capacity for the classes that use those bands). Where the exact vessel is unknown but the class is known, pick the size band that best represents the typical vessel on the route.
Why bigger ships are dramatically lower-carbon
The defining feature of the sea factor set is how steeply intensity falls as vessel size rises. A larger ship spreads its fuel burn over far more cargo, so the per-tonne-km emissions drop sharply. The chart below shows the effect for a bulk carrier on HFO across deadweight bands.
The RoPax ferry at 0.2579 kg CO₂e/tonne-km is the outlier — an order of magnitude above the cargo vessels — because it carries passengers alongside freight and runs on shorter, more frequent sailings with higher manoeuvring loads. Its bar is clipped in the chart above to keep the cargo-vessel contrast legible. The reporting lesson holds: vessel class matters as much as size, and a passenger-carrying RoPax is not interchangeable with a dedicated cargo RoRo even though both roll cargo on and off.
If a supplier reports only “shipped by sea” with no vessel detail, the size-band default matters enormously — a six-fold intensity swing sits between a small bulker and a Panamax. Where the cargo type points clearly to a vessel class, pick the size band that matches the typical vessel on that trade and flag it as a modelled default. Guessing the largest band to minimise the number is an audit finding; documenting a representative band is defensible.
Marine fuels — HFO, VLSFO, MDO, and IMO 2020
Non-container vessel rows carry three marine-fuel options. The choice reflects what the vessel actually burned, which since the IMO 2020 sulphur cap is most often VLSFO.
HFO — heavy fuel oil
The traditional residual bunker fuel. Still used by vessels fitted with exhaust scrubbers that allow continued high-sulphur burning. The default basis for the historical GLEC reference values.
VLSFO — very-low-sulphur fuel oil
The post-IMO-2020 default. The IMO sulphur cap that took effect in January 2020 limited marine fuel to 0.5% sulphur outside scrubber use, making VLSFO the prevailing fuel for most of the global fleet.
MDO — marine diesel oil
A distillate fuel, cleaner-burning than residual oils, common on smaller vessels and for manoeuvring in port. Note the GLEC slug is mdo (marine diesel oil), not the marine gas oil abbreviation.
The carbon-intensity differences between the three are modest relative to the swing driven by vessel size — fuel choice moves the needle by single-digit percentages, where a step up in vessel size band can halve the intensity. Select the fuel the vessel burned where it is known; where it is not, VLSFO is the defensible post-2020 default for most of the fleet.
The distance adjustment factor — out-of-route sailing
Ships do not sail in straight lines. They route around landmasses, queue for canals, follow established shipping lanes, and divert for weather. Great-circle port-to-port distance — the shortest path over the globe’s surface — therefore understates the actual distance sailed, and so understates tonne-km and emissions.
GLEC addresses this with a distance adjustment factor (DAF), publishing a distance-adjusted intensity that applies a roughly 15% uplift to account for out-of-route sailing. The calculator applies the distance you enter at face value, so the basis is in your hands:
- Actual sailed distance — if the carrier supplies the true distance sailed, enter it directly; no DAF adjustment is needed because the routing is already captured.
- Great-circle distance — if you have only the shortest-path port-to-port distance, apply the ~15% DAF uplift to the distance before entry to approximate the sailed distance.
Using raw great-circle distance with no DAF uplift systematically understates sea-freight emissions, and the gap is larger on lanes with significant detours — anything routing around a continent or through a congested canal approach. Document the distance basis per lane. An assurer will ask whether the distance is sailed, great-circle, or great-circle-plus-DAF, and an undocumented basis is a finding.
Worked example — a mixed bulk and container ocean shipment
This example reproduces against the live calculator. It deliberately combines a bulk leg and a container leg in one consignment — the realistic shape of an importer moving both raw material and finished goods — to demonstrate the rule that the two units are computed and reported separately and never merged. The two legs are shown in two distinct tables on two distinct units. All factors are GLEC Framework v3.2 well-to-wheel intensities.
Leg A — bulk cargo (tonne-km basis)
| Class / size / fuel | Mass | Distance | WTW intensity | Tonne-km | Emissions (kg CO₂e) |
|---|---|---|---|---|---|
| Bulk carrier · 60,000–100,000 dwt (Panamax) · HFO | 45,000 t | 11,000 km | 0.0052 kg/t-km | 495,000,000 | 2,574,000 |
Tonne-km = 45,000 × 11,000 = 495,000,000. Emissions = 495,000,000 × 0.0052 = 2,574,000 kg CO₂e (2,574 tCO₂e). The Panamax intensity of 0.0052 kg/t-km decomposes from the WTW headline; the small-bulker comparator at 0.0312 (WTT 0.0047 + TTW 0.0265) shows how much the size band matters.
Leg B — containerised cargo (TEU-km basis)
| Trade lane / type | TEU | Distance | WTW intensity | TEU-km | Emissions (kg CO₂e) |
|---|---|---|---|---|---|
| Trans-Pacific · dry | 120 TEU | 9,500 km | 0.0633 kg/TEU-km | 1,140,000 | 72,162 |
TEU-km = 120 × 9,500 = 1,140,000. Emissions = 1,140,000 × 0.0633 = 72,162 kg CO₂e (72.2 tCO₂e). The trans-Pacific dry lane at 0.0633 sits just below the container industry average of 0.0717; the reefer twin on the same lane (0.1287 kg/TEU-km) would roughly double the figure.
Shipment rollup — two activity totals, one emissions total
The two legs report 495,000,000 tonne-km and 1,140,000 TEU-km — two activity figures on two units that are never added together. Their emissions, however, do sum to a single 2,646.2 tCO₂e absolute footprint, because kilograms of CO₂e are unit-agnostic. This is the discipline the two-unit rule enforces: keep the activity and intensity figures separate, sum only the final emissions. The bulk leg dominates the footprint at 97% — moving 45,000 tonnes 11,000 km is far more transport activity than 120 containers across the Pacific, even though the bulk intensity per tonne-km is the lowest in the set.
Data quality and the GLEC default hierarchy
GLEC frames freight data quality as a hierarchy from primary measured energy down to modelled defaults. The reporting expectation is to climb the hierarchy where the emissions are material, not to apply the highest-precision method everywhere.
| Tier | Input shape | When it applies |
|---|---|---|
| Primary energy | Measured bunker fuel consumed on the voyage, converted via marine-fuel factors | Chartered or owned vessels, or a carrier that shares voyage fuel data — the most precise basis |
| Primary activity + modelled intensity | Actual mass/TEU and distance, with the GLEC class/size/lane intensity | The default for most reporting — actual activity, modelled factor. This calculator’s primary mode. |
| Modelled default | Actual activity with an industry-average container lane or a representative size-band default | Third-party legs where only mode, route, and rough volume are known |
| Distance estimate | Great-circle distance from port geocoding (with or without DAF), modelled intensity | The fallback where sailed distance is unavailable — flag as estimated, note the DAF basis |
The honest disclosure is the mix. A sea-freight inventory that runs primary fuel data on its chartered tonnage and modelled trade-lane averages on the spot-market container legs is a well-constructed inventory. Claiming primary-energy precision across every voyage when most are modelled lane averages is the disclosure failure, not the use of defaults.
Audit checklist — what gets flagged in sea-freight assurance
Sea-freight assurance under ISO 14083 and ISAE 3000 traces each leg from activity data to the rolled-up total. The findings below are the most common substantive issues raised on an ocean-freight inventory specifically.
01 — Tonne-km and TEU-km activity figures merged
The reviewer-trap finding. Adding a tonne-km total to a TEU-km total, or applying a TEU-km factor to a tonne-mass input. The two are different physical quantities. Each leg is computed on its own unit; only the final kg CO₂e outputs are summed.
02 — Reefer-bulk set beside container reefer as like-for-like
Refrigerated-bulk intensity (per tonne-km) and container reefer intensity (per TEU-km) both describe “reefer” emissions but on different units. Comparing or substituting one for the other misstates the result. Keep them on their respective unit bases.
03 — TTW reported instead of WTW
Reporting the combustion-only (tank-to-wheel) figure understates the footprint by the upstream fuel-production share. Scope 3 Category 4 requires the full well-to-wheel intensity. Confirm the headline factor is WTW, not TTW.
04 — Great-circle distance with no DAF basis stated
Using shortest-path distance without documenting whether a distance adjustment was applied understates sailed distance and emissions. The assurance team expects the distance basis — sailed, great-circle, or great-circle-plus-DAF — documented per lane.
05 — Size band chosen to minimise the number
Defaulting every unknown vessel to the largest, lowest-intensity size band understates emissions. Where the vessel is unknown, a representative band for the trade is defensible; the largest band as a blanket default is a finding.
06 — RoPax treated as cargo RoRo
RoPax ferries carry passengers alongside freight and run at an order-of-magnitude higher intensity than dedicated cargo RoRo. Selecting the cargo-RoRo class for a passenger-ferry leg materially understates the figure. Match the class to the actual vessel.
Reporting context — Scope 3, GLEC/ISO 14083, IMO, IFRS S2, CSRD
Sea-freight emissions feed several disclosure regimes through the same GLEC calculation. The four framework rows below cover the disclosure surface a typical shipper or carrier navigates; the IMO regulatory layer sits alongside as the maritime-sector context.
| Framework | Role for sea-freight emissions | Disclosure cadence |
|---|---|---|
| GHG Protocol Scope 3 Standard | The accounting standard. Defines Category 4 (upstream transport & distribution) and Category 9 (downstream) and sets the activity-data and average-data method options. | Same as the institution’s reporting cycle |
| GLEC Framework v3.2 | The methodology standard. Specifies the well-to-wheel intensities by vessel class, size band, trade lane, and marine fuel that this calculator applies. Aligned with ISO 14083, the international transport-chain emissions standard. | Annual factor refresh |
| IFRS S2 (ISSB) | The global disclosure baseline. Requires Scope 3 disclosure including transport categories where material, with the calculation methodology disclosed. | Annual, aligned with financial statements |
| CSRD ESRS E1 (EU) | The EU sustainability-reporting mandate. ESRS E1 requires Scope 3 disclosure for in-scope companies, with transport and distribution among the categories assessed for materiality. | Annual sustainability statement |
The IMO layer — CII and the maritime regulatory context
Distinct from the corporate-disclosure frameworks above, the International Maritime Organization regulates the carbon intensity of vessels directly. The IMO Carbon Intensity Indicator (CII) rates individual ships on their operational carbon intensity, and the IMO’s greenhouse-gas strategy sets fleet-wide reduction trajectories. These apply to the vessel operator, not to the shipper booking cargo — but they shape the fuel mix and vessel efficiency that feed back into the GLEC intensities a shipper reports. A shipper does not file under the CII; a carrier does. Understanding the distinction matters when a carrier cites its CII rating in response to a shipper’s emissions-data request — the CII is a vessel-efficiency rating, not a per-shipment financed-emissions figure.
GLEC and ISO 14083
GLEC v3.2 is structured to align with ISO 14083, the international transport-chain emissions methodology, so a calculation built on GLEC sea intensities is broadly ISO 14083-conformant. An ISO 14083 reference in a methodology statement signals an internationally standardised basis rather than a proprietary one, which assurers and disclosure regimes increasingly expect for transport emissions.
Data sources, factor versioning, and update transparency
Sea intensities — source and structure
The sea-freight intensities are drawn from GLEC Framework v3.2, retrieved for the MasterBrain factor set in May 2026. Sea is the deepest mode in the set: 211 rows across 11 vessel classes. The 10 non-container classes carry 135 rows on a per-tonne-km basis (vessel class × size band × marine fuel), and the container class carries 76 rows on a per-TEU-km basis (38 trade lanes × dry/reefer). Each row’s headline value is the well-to-wheel intensity on an AR6 GWP-100 basis; the well-to-tank and tank-to-wheel components and the distance-adjusted (DAF) values are published alongside and are reported as fixed figures in worked examples rather than user-variable inputs. See the DEFRA emission factors reference for the marine-fuel factors that complement the GLEC set for chartered-vessel primary-energy legs.
GWP basis
The GLEC sea set uses AR6 GWP-100 — the IPCC Sixth Assessment Report’s 100-year global warming potentials, the current GLEC convention, aligned with the GHG Protocol’s expected basis. Where sea-freight legs are combined with DEFRA-sourced own-vessel legs, note that DEFRA factors are published on an AR5 GWP-100 basis; the calculator does not silently reconcile the two, and a mixed-basis inventory should disclose the mix rather than implying a uniform basis. See the global warming potential definition for the AR5-to-AR6 distinction.
Versioning and update cadence
GLEC publishes factor refreshes annually, and the MasterBrain factor set tracks each publication. The calculator stamps each result with the MasterBrain version against which it was computed, so a leg computed against one factor vintage and the same leg recomputed against a later vintage are distinguishable in restatement work. The GLEC Framework version (v3.2) is independent of the underlying factor vintage — a methodology version applies across successive annual refreshes until the next framework revision ships.
What’s next — completing your Category 4 transport inventory
Sea freight is the dominant mode by tonnage in most international supply chains, but a complete Category 4 footprint spans every mode the chain uses. Each mode follows its own factor set and, in the case of sea, its own activity units. The road-freight calculator is live; the remaining modes are on the GreenCalculus build roadmap.
Live
Road Freight
GLEC v3.2 road set. Tonne-km × WTW intensity by region, class, load, and fuel. The sister calculator to this page.
Live
Sea Freight
GLEC v3.2 sea set. Per-tonne-km for bulk, tanker, and RoRo; per-TEU-km for container. The calculator on this page.
Live
Air freight
GLEC v3.2 air set. Bellyhold and freighter jet-fuel intensities by haul length.
Live
Rail freight
GLEC v3.2 rail set. Diesel and electric traction by commodity profile.
Live
Last-mile delivery
Van and small-vehicle factors — per kilometre, not per tonne-km. A different unit basis again.
Live
Cold-chain logistics
Refrigerated freight adds reefer-energy and refrigerant-leakage components on top of the transport intensity.
Live
GHG Inventory Aggregator
Roll Category 4 together with every other Scope 1, 2 and 3 source into one auditable corporate carbon footprint — the organisation-level inventory this category feeds into.
Separately from the upstream Category 4 modes above, downstream transport and distribution — the movement of sold products after they leave the company’s control — is accounted under Scope 3 Category 9, not Category 4. It uses the same GLEC sea intensities but books to a different category line. A dedicated downstream transport calculator is on the roadmap and is not yet published.
Quick converter: g CO₂e/tonne-km to per tonne-nautical-mile.
Frequently asked questions
Because the cargo types are allocated differently. Bulk, tanker, RoRo, and general cargo are priced per tonne-kilometre — mass × distance — because the vessel carries a measurable cargo mass. Containerised cargo is priced per TEU-kilometre, because a container ship carries the goods of hundreds of shippers and the only tractable allocation is per container-slot-kilometre, regardless of what is inside each box. The two units describe different physical quantities and are never summed.
No. Tonne-km and TEU-km are different physical quantities and must never be added or compared directly. A mixed shipment with both bulk and container legs is reported as two separate activity totals on two separate units. What does sum is the final emissions: once each leg’s kg CO₂e is computed, those figures add into one absolute footprint, because kilograms of CO₂e are unit-agnostic. Keep the activity figures and intensities separate; sum only the emissions outputs.
A larger vessel spreads its fuel burn over far more cargo. A bulk carrier under 10,000 dwt on HFO runs at 0.0312 kg CO₂e/tonne-km; a 60,000–100,000 dwt Panamax on the same fuel runs at 0.0052 — roughly six times lower. This economies-of-scale effect is the single largest driver of intensity in the sea set, larger than the choice of marine fuel. Selecting the right size band matters more than almost any other input.
A TEU is a twenty-foot equivalent unit — the standard measure of container capacity. A standard 20-foot container is one TEU; a 40-foot container is two TEU. Container sea-freight intensity is expressed per TEU-kilometre, so the activity input is the number of TEU multiplied by the over-water distance. Count a 40-foot box as two TEU when entering container activity.
Select the lane that matches the route — the GLEC set carries 38 trade lanes including the trans-Atlantic, trans-Pacific, and Suez corridors. The trade-lane average embeds the typical vessel mix on that route, so there is no separate vessel-size or fuel input for containers. Where the specific lane is unknown, the industry-average row (dry 0.0717, reefer 0.1423 kg CO₂e/TEU-km) is the defensible default. Choose dry or reefer to match whether the container is refrigerated.
Ships do not sail in straight lines — they route around landmasses, through canals, and along shipping lanes — so great-circle port-to-port distance understates the actual distance sailed. GLEC publishes a distance-adjusted value applying a roughly 15% uplift to account for out-of-route sailing. If you have the actual sailed distance from the carrier, enter it directly. If you have only great-circle distance, apply the DAF uplift before entry. Document which basis you used per lane.
Select the fuel the vessel actually burned. HFO (heavy fuel oil) is the traditional residual bunker fuel, still used by scrubber-fitted vessels. VLSFO (very-low-sulphur fuel oil) became the default for most of the fleet after the IMO 2020 sulphur cap. MDO (marine diesel oil) is a cleaner distillate common on smaller vessels. The carbon-intensity differences between the three are modest relative to the swing from vessel size. Where the fuel is unknown, VLSFO is the defensible post-2020 default. Container rows carry no fuel input — the trade-lane average reflects the prevailing mix.
The calculator computes both identically — the GLEC sea intensities are the same. The difference is the direction of the goods flow and the category line the result is booked to. Category 4 is upstream transport the reporting company pays for, bringing goods in. Category 9 is downstream transport of sold products after they leave the company’s control. Use this calculator for either and book the result to the correct category for your reporting boundary.
The IMO Carbon Intensity Indicator (CII) applies to the vessel operator, not to a shipper booking cargo. It rates individual ships on operational carbon intensity. A shipper computing Scope 3 Category 4 emissions reports per-shipment financed emissions using the GLEC activity-based method, not the CII. The two are related — a carrier’s CII reflects the efficiency that feeds into the GLEC intensities — but a CII rating is not a per-shipment emissions figure and does not substitute for the Category 4 calculation.
The GLEC sea set uses AR6 GWP-100 — the IPCC Sixth Assessment Report’s 100-year global warming potentials, the current GLEC convention. Where sea-freight legs are combined with DEFRA-sourced own-vessel legs, note that DEFRA factors are AR5 GWP-100; the calculator does not silently reconcile the two bases, and a mixed-basis inventory should disclose the mix rather than implying a uniform basis.
Methodology notes and limitations
Methodology version. Calculator implements the GLEC Framework v3.2 sea-freight intensities (retrieved May 2026), aligned with ISO 14083. Results are computed on an AR6 GWP-100 basis. Inventories computed against earlier factor vintages remain auditable against the corresponding MasterBrain version stamp.
Mode boundary. Sea freight only — the 10 non-container vessel classes (bulk carrier, oil and chemical tankers, general cargo, liquefied-gas and other-liquids tankers, RoPax, refrigerated bulk, RoRo, vehicle carrier) plus containerised cargo. Road, air, rail, inland-waterway, and cold-chain freight use separate factor sets and are out of scope.
Two unit bases. Non-container cargo is per tonne-kilometre; containerised cargo is per TEU-kilometre. The two are different physical quantities. The calculator computes them separately and never merges the activity figures or the intensities; only the final kg CO₂e outputs are summed. Refrigerated-bulk (tonne-km) and container reefer (TEU-km) are not interchangeable.
WTW headline; WTT/TTW and DAF fixed components. The calculator computes the well-to-wheel total. The well-to-tank and tank-to-wheel components and the distance-adjusted (DAF) value are published by GLEC alongside each row and are reported as fixed figures; they do not vary with user inputs and are not separate live fields.
Distance basis. The calculator applies the distance entered at face value. Sea distances should be either actual sailed distance from the carrier, or great-circle distance with a DAF uplift applied before entry. Document the basis per lane; raw great-circle distance with no DAF understates emissions.
Vessel size matters most. Intensity falls roughly six-fold across the bulk-carrier deadweight bands. Where the vessel is unknown, select a representative size band for the trade and flag it as a modelled default; do not default to the largest, lowest-intensity band as a blanket assumption.
Activity data taken as entered. The calculator uses the mass, TEU, and distance the user enters; it does not independently verify them. The user is responsible for the activity-data basis and the distance basis, and for documenting both per leg.
No assurance opinion. 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, or other regulatory submissions. The full methodological deep-dive — vessel-class selection, the size-band intensity curves, the container trade-lane structure, the DAF derivation, and the tonne-km-versus-TEU-km handling — is published on the paired GLEC sea-freight methodology page.