Product LCA · Break-Even · Reusable vs Single-Use
Reusable vs Single-Use Carbon Comparison Calculator
Work out how many uses it takes for a reusable item to beat its single-use equivalent on carbon — the break-even point — by comparing cradle-to-gate embodied carbon against the per-use footprint of each system, including the energy and water of washing. Built on DEFRA material factors and a modelled wash cycle, reported at consumer scale in kg CO₂e.
The break-even question. A reusable item almost always carries more embodied carbon than the single-use item it replaces — a steel bottle against a thin PET one, a heavy ceramic-lined cup against a paper one. It only pays that carbon back through use. This calculator computes the number of uses at which the reusable’s cumulative footprint drops below the single-use system it displaces: the carbon break-even point.
The break-even identity. Break-even uses = embodied carbon of the reusable ÷ (single-use footprint per use − reusable footprint per use). The numerator is the reusable’s cradle-to-gate embodied carbon. The denominator is the net carbon saved each time you use the reusable instead of a single-use item — which is the single-use item’s own embodied carbon minus the wash burden the reusable adds each cycle. When the denominator is zero or negative, the reusable never breaks even, and the calculator says so rather than printing a misleading number.
Embodied carbon comes from DEFRA material factors. Both sides are built from the same source: the material’s cradle-to-gate (A1–A3) embodied factor multiplied by the item’s mass. The user picks a material — stainless steel, aluminium, container glass, or one of the common plastics (PP, PET, HDPE, PS, LDPE/LLDPE, PVC) and paper/board — and enters a mass for each side. Recycled content is applied as a virgin-to-recycled blend of the DEFRA factors, not as an end-of-life credit.
Washing is modelled, not guessed. The use-phase burden of the reusable is a real calculation, not a flat assumption. Three wash methods are offered — dishwasher, a filled basin, and a running tap — each with reference energy and water intensities from the MasterBrain. The dishwasher cycle is shared across a full load (default 14 place settings) and allocated per item; water heating is already inside the per-cycle energy figure. Wash carbon is the energy times the location-based grid factor plus the water times its supply-and-treatment factor. “Not washed” sets the wash burden to zero.
Boundary — cradle-to-gate plus washing. The default boundary is cradle-to-gate embodied carbon (A1–A3) plus the use-phase wash. An optional, off-by-default end-of-life line adds an indicative disposal figure using a construction-waste combustion proxy — flagged as indicative because the MasterBrain holds no product-specific end-of-life factors for these items. Transport, retail, and loss or breakage are out of scope in this version; instead of a breakage rate, you set the number of uses you expect to get, and the tool warns if break-even falls beyond it.
What this tool does not cover. It compares a material against a material by mass. It is not a textile tool — cotton tote bags and reusable nappies are outside its scope, because the MasterBrain carries no fabric embodied factor for them. The four scenario presets (bottle, cup, bag, container) only pre-fill material and mass; nothing is category-locked, and the honest answer for a given item depends entirely on the masses and wash method you enter.
Advanced assumptions — recycled content, wash intensity, end-of-life
Break-even over uses: how many times you must reuse an item before it beats its single-use equivalent. Embodied carbon (A1-A3) from DEFRA 2026 materials × your product mass; wash burden from EU Ecodesign dishwasher benchmarks and Energy Saving Trust / Which? hand-wash figures × the grid and water factors. Material + mass model — reads MasterBrain V3 live. AR5 GWP-100.
Pick a scenario, then Compare
Results show the break-even number of uses, a cumulative-emissions crossover chart, a lifecycle breakdown, wash-method sensitivity, audit trail and export.
Results are indicative and compare typical materials at the masses you enter — not specific branded products. Embodied factors are DEFRA 2026 cradle-to-gate (A1-A3, AR5 GWP-100); wash-cycle energy and water are EU Ecodesign eco-programme benchmarks (dishwasher) and Energy Saving Trust / Which?-derived figures (hand washing), the latter behaviour-dependent and surfaced as editable assumptions. The break-even depends heavily on product mass, wash method and grid — weigh your items and confirm the wash assumptions before relying on the result. Textiles, ceramics, detergent and product transport are out of scope in this version; end-of-life is an indicative construction-waste proxy. Verify against your own data before using for reporting or procurement decisions.
A reusable bottle is a carbon loan. It arrives already in debt — a stainless-steel body carries far more embodied carbon than the flimsy plastic bottle it is meant to replace — and it repays that debt one use at a time, each refill saving the carbon of a single-use bottle not bought. Use it enough and it comes out ahead. Abandon it in a drawer after a fortnight and it never does.
Whether a reusable actually beats single-use is not a slogan — it is an arithmetic break-even that depends on mass, material, and how you wash it.
A reusable item breaks even on carbon once its uses cover its extra embodied carbon versus single-use. A steel water bottle typically breaks even around 40–50 uses; a reusable cup can take 15–20 washes — or never, if washed under a hot running tap that costs more than the cup it replaces.
What the comparison actually measures
This calculator answers one question: how many uses does a reusable item need before its total carbon footprint drops below the single-use equivalent it replaces? That crossover — the break-even point — is the honest unit of a reusable-versus-disposable comparison. Below it, the reusable is the higher-carbon choice; above it, the lower-carbon one. The number is not fixed by the object alone: it moves with the mass of each item, the material, and how the reusable is washed.
Break-even is measured in uses, not units
The common mistake is to compare one reusable item against one single-use item and conclude the reusable “wins” because it lasts. That compares the wrong things. The correct functional unit is a use — one drink served, one shopping trip carried — because that is what each system delivers. A reusable bottle used 500 times is compared against 500 single-use bottles, and the wash carbon of those 500 uses is counted against the reusable. Framing the comparison per-use rather than per-item is the discipline that makes the answer meaningful.
A reusable is not automatically the greener choice. It carries a larger embodied-carbon debt up front and adds a small wash burden every cycle, so it only comes out ahead after enough uses to repay the debt. A reusable used a handful of times and discarded is worse for the climate than the single-use items it replaced — the environmental case for reusables is entirely a case about actually reusing them.
Where this sits — product LCA and the waste hierarchy
The comparison is a small, focused product life-cycle assessment: two systems, a shared functional unit, a cradle-to-gate boundary plus use-phase washing. It draws on the same embodied-carbon logic as a full product footprint, and it maps onto the waste hierarchy’s preference for reuse over single-use — but only once the break-even is cleared. For an organisation, the result feeds procurement decisions and, when reusables replace purchased single-use stock, the Scope 3 Category 1 line of a corporate inventory.
How the calculation works — the break-even identity
The whole comparison reduces to one division: a fixed carbon debt over the net saving per use.
Break-even (uses) = Reusable embodied carbon ÷ (Single-use footprint per use − Reusable wash footprint per use)
The numerator — the reusable’s embodied carbon
The reusable’s embodied carbon is its material’s cradle-to-gate (A1–A3) factor multiplied by its mass. A stainless-steel bottle at a few hundred grams carries a debt of a couple of kilograms of CO₂e; a light plastic cup, a fraction of that. The calculator reads the DEFRA material factor live and applies the mass you enter, blending virgin and recycled factors in proportion to the recycled content you set. One thing to watch: the underlying factors are stored on a mixed basis — plastics, container glass, and paper are held per tonne, while steel and aluminium are per kilogram — and the engine reconciles that internally, so the mass you enter is always in grams at the interface.
The denominator — net saving per use
Each use of the reusable avoids one single-use item’s embodied carbon but adds the reusable’s wash burden. The net saving per use is therefore the single-use item’s per-use footprint minus the wash footprint of one cycle. This is where a comparison can quietly fail: if the wash burden of the reusable exceeds the embodied carbon of the single-use item it replaces, the denominator is zero or negative and the reusable never breaks even. The calculator surfaces that as an explicit “never breaks even” result rather than an implausibly large number of uses.
Comparing one reusable against one single-use item — rather than the reusable against as many single-use items as it replaces — is the error that makes reusables look free. Every use of the reusable must carry its share of the wash burden, and the single-use side must be counted once per use. A reusable that is barely used, or washed extravagantly, can lose the comparison outright; the per-use framing is what exposes that instead of hiding it.
The wash phase — where reusables win or lose
For most reusables the embodied carbon is fixed at manufacture, so the variable that decides the comparison is the wash. It is the one input a naïve comparison ignores and the one that most often flips the result. The calculator models three wash methods, each with its own energy and water intensity, and lets you override every value.
Dishwasher (shared load)
A full cycle’s energy and water are shared across the load — a default of 14 place settings — and allocated per item. Per-item burden is low precisely because it is shared, so a dishwasher run near-full is usually the lowest-carbon wash for a reusable. Water heating is already inside the per-cycle energy figure.
Filled basin
A basin of hot water washing a batch of items by hand. Per-item energy and water sit between the dishwasher and the running tap. A reasonable middle case, and often the real-world default in a household without a dishwasher.
Running tap (hot)
Washing each item under a continuously running hot tap. The highest-carbon method by a wide margin, because the water is heated and none of it is shared. This is the method that can push a light reusable past the point of ever breaking even.
The grid factor of the wash matters too
Wash carbon is dominated by the energy to heat water, and that energy carries the location-based grid factor of wherever the washing happens. On a clean grid the wash burden is small and break-even comes quickly; on a dirtier grid the same wash costs more carbon per cycle and pushes break-even further out. The calculator reads the grid factor for the chosen country, so the wash burden is grid-appropriate rather than a fixed figure.
The single biggest lever a user controls is the wash method. Running a dishwasher full rather than washing each item under a hot tap can be the difference between a reusable that breaks even in a couple of dozen uses and one that never does. Where behaviour allows, a cold or shared wash beats any change of material — the use-phase, not the embodied carbon, is where a marginal reusable is won or lost.
What’s in the boundary — cradle-to-gate scope
A break-even number is only as honest as the boundary behind it. This calculator is explicit about what it counts and what it leaves out, so the result is not over-claimed.
| Life-cycle stage | Included? | How it’s handled |
|---|---|---|
| Raw materials & manufacture (A1–A3) | Yes | DEFRA cradle-to-gate factor × mass, both sides; virgin/recycled blend by recycled content |
| Use phase — washing | Yes | Modelled per wash method (dishwasher / basin / tap), grid- and water-factored |
| End-of-life | Optional, off by default | Indicative disposal proxy only — no product-specific factor exists; flagged indicative |
| Transport & retail | No | Out of scope in v1 |
| Loss & breakage | No | No breakage rate; instead set an expected-uses horizon and the tool warns if break-even exceeds it |
Recycled content is a blend, not a credit
Setting a recycled-content percentage blends the virgin and recycled DEFRA factors for the material in proportion — it lowers the embodied numerator directly. It is not applied as an end-of-life recycling credit, which would be a separate and more contestable accounting choice. This keeps the embodied figure attributional and avoids double-counting a benefit at both ends of the life cycle. For the allocation questions that recycling credits raise, the PCF allocation methods calculator is the dedicated tool.
The optional end-of-life line uses an indicative disposal proxy, not a product-specific factor — the MasterBrain holds no cradle-to-grave end-of-life factor for these items. Leave it off for a defensible cradle-to-gate-plus-wash comparison; switch it on only for a rough sense of disposal’s direction, and never quote the end-of-life-inclusive figure as a precise result.
Inputs this calculator needs — and where to source them
Each side of the comparison takes a material and a mass; the wash method and horizon complete the model. A scenario preset fills the material and mass fields with a sensible starting pair, but every field is editable, and the mass is the input most worth getting right — it scales the entire embodied figure.
| Input | Unit | Source | Notes |
|---|---|---|---|
| Reusable material & mass | material · g | User; weigh the item | Mass scales embodied carbon linearly — worth measuring, not guessing |
| Single-use material & mass | material · g | User; weigh the item | The per-use item the reusable replaces |
| Recycled content | % | User; product spec or default 0 | Blends virgin/recycled DEFRA factors on the embodied side |
| Wash method | dishwasher / basin / tap / none | User | The dominant use-phase lever; reference intensities from the MasterBrain |
| Location / grid | country | User | Sets the grid factor behind the wash energy |
| Compare over N uses | uses | User | The horizon; tool warns if break-even falls beyond it |
| Include end-of-life | on / off | User; default off | Indicative disposal proxy only |
Weigh both items on a kitchen scale rather than estimating. Embodied carbon scales directly with mass, so a 20% error in the mass of the reusable is a 20% error in its break-even point. A single-use item’s mass is easy to underestimate — a “thin” PET bottle and a sturdier one differ enough to move the comparison — so measure the specific items you are actually comparing.
Worked example — a steel bottle, and the wash-method flip
Both examples below reproduce to the digit against the live calculator (MasterBrain v2026.29). The first is the tool’s default case; the second shows how completely the wash method can govern the answer — the calculator’s signature honest result.
The default — steel bottle vs PET bottle
A stainless-steel bottle weighing 320 g, washed in a dishwasher on the UK grid, compared against a 15 g single-use PET bottle with no recycled content, one bottle per use.
| Component | Value (MB v2026.29) |
|---|---|
| Reusable embodied carbon (steel, 320 g) | 2.20 kg CO₂e |
| Single-use footprint per use (PET, 15 g) | 0.0580 kg CO₂e |
| Reusable wash footprint per use (dishwasher, UK) | 0.0077 kg CO₂e |
| Net saving per use | 0.0502 kg CO₂e |
| Break-even | 44 uses |
The steel bottle starts 2.20 kg in debt. Each use avoids a 0.0580 kg PET bottle but adds 0.0077 kg of dishwasher wash, netting 0.0502 kg saved per use. Dividing the debt by that saving gives a break-even of 44 uses — a little over six weeks at daily use. Beyond that, the reusable pulls steadily ahead:
| Uses | Reusable cumulative | Single-use cumulative | Outcome |
|---|---|---|---|
| 1 | 2.21 kg | 0.06 kg | Single-use ahead |
| 44 | ≈ 2.54 kg | ≈ 2.55 kg | Break-even |
| 500 | 6.07 kg | 29.0 kg | Reusable 79% lower — saves 22.9 kg |
At 500 uses the steel bottle has a cumulative footprint of 6.07 kg against 29.0 kg for 500 PET bottles — a 79% reduction, saving 22.9 kg of CO₂e. The debt that looked large at use one is trivial across a realistic lifetime of refills. This is the reusable case working as intended: a modest embodied debt repaid many times over.
The flip — a light cup washed three ways
Now the counter-case. A reusable polypropylene cup weighing 45 g, compared against a 12 g paper cup, with everything held constant except the wash method:
| Wash method | Wash per use | Break-even |
|---|---|---|
| Filled basin | low | 16 uses |
| Dishwasher (shared load) | low | 18 uses |
| Running hot tap | 0.0172 kg | Never breaks even |
Washed in a basin the PP cup breaks even in 16 uses; in a dishwasher, 18. But under a running hot tap the wash costs 0.0172 kg of CO₂e per use — more than the 0.0144 kg embodied in the paper cup it is meant to replace. The net saving per use goes negative, and the reusable never breaks even, no matter how many times it is used. Same cup, same paper alternative, same everything — only the tap changed, and it inverted the entire conclusion.
The running-tap result is not an edge case to hide — it is the most useful thing the calculator says. A light reusable washed wastefully can be worse than the single-use item it replaces, permanently. This is why a blanket “reusables are better” claim is unsafe, and why the break-even framing, with the wash method exposed as an input, is the honest way to answer the question.
Reading the result — break-even, lifetime delta, sensitivity
The calculator returns three things worth reading together: the break-even point, the cumulative delta at your chosen horizon, and how break-even shifts across wash methods. The embedded crossover chart plots both systems’ cumulative carbon against uses, marking the break-even crossing, so the relationship is visible rather than inferred.
Three result shapes
Break-even is reported as one of three honest outcomes rather than always as a number:
- A number of uses — the normal case: the reusable repays its embodied debt after N uses (rounded up to a whole use).
- “From use 1” — the reusable is lower-carbon immediately, because its embodied carbon is already below the single-use item’s per-use footprint. Rare, but real for a light reusable against a heavy single-use item.
- “Never breaks even” — the wash burden per use meets or exceeds the single-use item’s per-use footprint, so the net saving is zero or negative. No number of uses would help.
What moves the number — a sensitivity ranking
The inputs are not equal in leverage. In rough order of how hard each swings the break-even point:
- Wash method — the dominant use-phase lever; can move break-even from a dozen uses to never.
- Reusable mass and material — sets the embodied debt; a heavier or higher-carbon reusable takes proportionally longer.
- Single-use mass — the thing being replaced; a heavier single-use item means a larger saving per use and a faster break-even.
- Grid factor (location) — scales the wash burden; a dirtier grid pushes break-even out.
- Recycled content — trims the embodied numerator; real but second-order versus the wash.
Read the break-even point against your expected uses, not in isolation. A 44-use break-even is excellent for a daily-use bottle kept for years and irrelevant for a promotional cup used twice and lost. The calculator’s expected-uses horizon exists for exactly this reason: a reusable only delivers its saving if it is actually used past its break-even, and setting an honest horizon is what turns the number into a decision.
Standards and reporting context
The comparison is a focused product LCA, and it draws on the standards that govern life-cycle carbon accounting. None mandate a break-even calculation, but they define the boundary, the functional unit, and the factor basis the result rests on.
| Framework | Role in the comparison |
|---|---|
| ISO 14040 / 14044 | The LCA framework — functional unit, system boundary, and the principle that comparison is per-function (per use), not per-item. |
| ISO 14067 | The product carbon footprint standard — quantifying the cradle-to-gate embodied carbon of each item on a consistent basis. |
| GHG Protocol Product Standard | The corporate-facing product accounting standard; where a reusables switch lands in an organisation’s product-level reporting. |
| PAS 2050 | The BSI product life-cycle GHG specification underpinning much consumer-goods carbon work. Cited as a named basis; no dedicated GreenCalculus standards page. |
| GHG Protocol Scope 3 Standard | Where an organisational reusables programme reports — Category 1 for purchased goods, and Category 5 where single-use waste is avoided. |
The embodied side shares its material factors with the wider embodied-carbon toolset — the same DEFRA factors drive the embodied carbon of plastics and packaging. For the full cradle-to-grave version of this kind of comparison, the ISO 14067 cradle-to-grave calculator extends the boundary beyond the gate.
Data sources, factor versioning, and update transparency
Material embodied factors — DEFRA
Both sides’ embodied carbon comes from DEFRA cradle-to-gate (A1–A3) material factors, read live from the MasterBrain and applied to the mass you enter, with a virgin-to-recycled blend where recycled content is set. The factors are stored on a mixed basis — plastics, container glass, and paper per tonne; steel and aluminium per kilogram — which the engine reconciles internally so the interface always takes grams. The factors carry AR5 GWP-100 as DEFRA publishes them.
Wash energy and water
| Wash reference (MB v2026.29) | Value |
|---|---|
| Dishwasher energy per cycle | 0.80 kWh |
| Dishwasher water per cycle | 9.5 L |
| Dishwasher place settings per cycle | 14 |
| Wash carbon basis | Energy × location-based grid factor + water × (mains supply + wastewater treatment) |
The wash reference intensities live in a dedicated MasterBrain section built for this calculator; water heating is already inside the per-cycle energy figure, and the dishwasher cycle is allocated per item across the place-setting count. The grid factor is the location-based electricity factor for the chosen country, the same factor the Scope 2 Electricity Calculator applies to purchased power. Every reference value is editable in the advanced drawer.
Versioning and basis
Material and grid factors update on DEFRA’s annual cycle. The calculator stamps each result with the MasterBrain version, so a result computed against one vintage is distinguishable from the same inputs run against a later one. A basis note: these DEFRA factors are AR5 GWP-100, whereas corporate inventories default to AR6 — the asymmetry is inherited from the source data, not introduced here, and matters only if you are reconciling this consumer-scale figure against an AR6 inventory line.
What’s next — from comparison to Scope 3
A single reusable-versus-single-use comparison answers a procurement or personal question. The adjacent questions — the full life cycle, where the saving lands in a corporate inventory, and how it compares to other break-even decisions — have their own tools.
The full life cycle
To extend the boundary past cradle-to-gate to a complete cradle-to-grave footprint, the ISO 14067 cradle-to-grave calculator adds the downstream stages this tool leaves out.
The embodied side in depth
The plastics and packaging embodied-carbon calculator details the single-use material footprints that sit on one side of this comparison.
Where it lands in Scope 3
An organisational switch to reusables changes purchased-goods and waste lines. The Scope 3 Standard defines Category 1 (purchased goods) and Category 5 (waste), where the saving is reported.
Other break-even decisions
The same embodied-versus-operational crossover logic drives the solar carbon payback and EV vs petrol lifecycle calculators — different domains, identical break-even arithmetic.
The full methodology — the break-even derivation, the wash model, the virgin-recycled blend, and the boundary choices — is documented on the paired Reusable vs Single-Use LCA methodology page.
Frequently asked questions
It depends on the material, the mass, and how you wash it — that is what the calculator computes. As a guide, a stainless-steel water bottle typically breaks even against single-use plastic around 40–50 uses, and a light reusable cup around 15–20 washes. But the number is not fixed: a heavier reusable takes longer, and a wasteful wash can push break-even out indefinitely. Enter your actual items and wash method for a specific answer rather than relying on a rule of thumb.
No. A reusable carries more embodied carbon up front and adds a wash burden each use, so it only comes out ahead after enough uses to repay that debt. A reusable used a handful of times and discarded is worse than the single-use items it replaced. And a light reusable washed under a hot running tap can cost more carbon per wash than the single-use item it replaces, so it never breaks even at all. The environmental case for reusables is a case about actually reusing them, washed efficiently.
It can, in the worst case. Washing adds a small carbon burden to every use of a reusable, dominated by the energy to heat water. A shared dishwasher load or a filled basin keeps that burden low; a continuously running hot tap makes it large. For a light reusable against a light single-use item, a hot-tap wash can exceed the single-use footprint entirely, so the reusable never breaks even. Wash method is the single biggest lever the user controls.
Per use, not per item. The correct functional unit is one use — one drink, one trip — because that is what each system delivers. A reusable used 500 times is compared against 500 single-use items, with the wash carbon of all 500 uses counted against the reusable. Comparing one reusable against one single-use item makes the reusable look free by ignoring how many disposables it actually replaces and the wash burden it accumulates.
From DEFRA cradle-to-gate (A1–A3) material factors, read live from the MasterBrain and multiplied by the mass you enter. Recycled content is applied as a virgin-to-recycled blend of those factors, lowering the embodied figure directly rather than as an end-of-life credit. The factors are stored on a mixed basis (plastics, glass, and paper per tonne; steel and aluminium per kilogram) which the engine reconciles internally, so you always enter mass in grams.
Only as an optional, off-by-default indicative line. The default boundary is cradle-to-gate embodied carbon plus the use-phase wash. An end-of-life toggle adds a rough disposal proxy, flagged as indicative because the MasterBrain holds no product-specific end-of-life factor for these items. Leave it off for a defensible comparison; switch it on only for a rough sense of disposal’s direction, not a precise figure. For a full downstream boundary, use the ISO 14067 cradle-to-grave calculator.
Not in this version. The calculator compares a material against a material by mass, using the embodied factors the MasterBrain carries — stainless steel, aluminium, container glass, and the common plastics and paper/board. It holds no textile embodied factor, so cotton totes and reusable nappies are out of scope. The scenario presets cover bottles, cups, bags, and containers made from the supported materials.
Because the net saving per use is zero or negative. If the wash burden of the reusable meets or exceeds the per-use footprint of the single-use item it replaces, no number of uses will make the reusable come out ahead. This happens with a light reusable washed wastefully — for example a hot running tap costing more per wash than the paper cup it replaces. The calculator reports this honestly instead of printing an implausibly large break-even number.
Yes, on the embodied side. Setting a recycled-content percentage blends the virgin and recycled DEFRA factors in proportion, lowering the embodied carbon of that item and, for a reusable, bringing its break-even point forward. The effect is real but generally second-order compared with the wash method and the item masses. It is applied as a blend of embodied factors, not as an end-of-life recycling credit.
Methodology notes and limitations
What break-even means here. The number of uses at which the reusable’s cumulative footprint (embodied plus accumulated wash) drops below the single-use system’s cumulative footprint over the same number of uses. Reported as a whole number of uses (rounded up), or as “from use 1” or “never breaks even” where those are the honest outcomes.
Boundary is cradle-to-gate plus washing. Embodied carbon is DEFRA cradle-to-gate (A1–A3) material factor × mass, both sides. The use phase is the modelled wash. End-of-life is an optional, off-by-default indicative proxy — no product-specific factor exists. Transport, retail, and loss/breakage are out of scope in v1.
Recycled content is a factor blend. Recycled content blends virgin and recycled DEFRA factors on the embodied side; it is not applied as an end-of-life recycling credit. The embodied figure stays attributional and avoids double-counting.
Wash is modelled from reference intensities. Three methods (dishwasher, filled basin, running tap) with MasterBrain reference energy and water figures, the dishwasher allocated per item across a default 14-place-setting load. Water heating is inside the per-cycle energy. All values are editable; “not washed” sets the wash burden to zero.
Material, not category. The tool compares a material against a material by mass. It carries no textile factor, so cotton totes and reusable nappies are unsupported. The four scenario presets pre-fill material and mass only — nothing is category-locked, and the result always depends on the masses and wash method entered.
GWP basis. DEFRA material and grid factors are AR5 GWP-100 as published. Corporate inventories default to AR6; reconcile the basis if comparing this consumer-scale figure against an AR6 inventory line.
Worked-example provenance. Both worked examples reproduce to the digit against the live engine at MasterBrain v2026.29. If the MasterBrain revises the underlying factors, the figures should be re-pulled before being quoted as current.
Not an assurance opinion. Results are estimates for comparison and communication, not a verified LCA or an assurance opinion. A full ISO 14040/44 study with primary data should replace these defaults before a comparison is used in a published product claim or a procurement mandate. The full methodology is on the Reusable vs Single-Use LCA methodology page.