Methodology
This calculator gives rough estimates, not a scientific carbon audit. This page explains how those estimates are calculated, where the numbers come from, and where they fall short.
What is CO₂e?
CO₂e, or carbon dioxide equivalent, is a unit for expressing the combined warming effect of different greenhouse gases (carbon dioxide, methane, nitrous oxide, and others) as a single number, based on their relative warming potential. That lets emissions from very different activities, like driving, flying, and eating beef, get added together and compared on the same scale.
How the calculation works
For each category, the app multiplies your reported activity (miles driven, kWh used, meals eaten, and so on) by a published emissions factor: the amount of CO₂e produced per unit of that activity. Category totals are added together for your overall footprint. All calculations are pure, deterministic functions, so the same inputs always produce the same output. None of it is calculated by AI or estimated qualitatively.
The interface itself never performs a calculation. It calls into a separate calculation engine (src/climate/calculations) with its own test suite, which reads from local, versioned data files (src/data/*.json). Nothing is fetched from EPA, OWID, or DEFRA at runtime.
Key assumptions
- You report trips, not distances, so a domestic round trip is assumed to cover 2,510 km (about twice the average one-way US domestic flight) and an international round trip 12,000 km (a long-haul trip like US-Europe or US-Asia). Your actual trips may be shorter or longer.
- Beef and chicken per-meal figures assume a 150 g cooked serving, converted from published per-kilogram food footprints.
- Vegetarian and vegan meals use a different method: whole-diet daily averages from a UK dietary study, divided by an assumed 3 meals a day. No equivalent per-meal dataset was available for these.
- Electricity uses a national-average grid intensity for the country you select on the “Your region” step (US average by default). If you pick a US state, a state-level factor is used instead (see the US state table below) — but outside the US, intensity still only varies by country, even though it also varies by province/region there in reality. Region selection currently only affects electricity (and EV charging); other categories still use general averages regardless of location.
- SUV/truck and hybrid factors are derived approximations (see the factor table below), not numbers EPA publishes directly per mile.
- Clothing and electronics factors are rough, blended estimates. Per-item footprints vary enormously by product, and this MVP doesn't try to model that variation.
Limitations
- This is an MVP covering five everyday categories. It isn't an exhaustive inventory of every possible emissions source.
- Factors marked “rough estimate” below are placeholders, used where a precise, confidently sourced number wasn't available, rather than an invented number that just looks precise.
- Results are shown in rounded tonnes to avoid implying false precision. Internally, calculations use full decimal precision.
- Your data is estimated, self-reported, and never checked against any outside record.
Emission factors and sources
Every number used anywhere in this app traces back to one of these factors.
Transportation
| Factor | Value | Source | Year |
|---|---|---|---|
| Average gasoline car EPA's published on-road average for a typical gasoline passenger vehicle, derived from average fuel economy and per-gallon tailpipe CO2, CH4, and N2O emissions. | 0.404 kg / mile | US EPA Greenhouse Gas Equivalencies Calculator | 2024 |
| Gasoline SUV or truck Derived by scaling the EPA average passenger vehicle factor (0.404 kg/mile) by the ratio of the model-year-2024 fleetwide average fuel economy (27.2 mpg) to the truck-SUV average (25.7 mpg), per the EPA Automotive Trends Report. This is an approximation, not a directly published EPA per-mile SUV/truck factor. | 0.428 kg / mile | US EPA Greenhouse Gas Equivalencies Calculator + EPA Automotive Trends Report | 2024 |
| Hybrid carRough estimate PLACEHOLDER: no single official EPA per-mile hybrid factor was available. Estimated as ~60% of the average gasoline car factor, reflecting the commonly reported ~40% fuel-economy improvement of hybrids over conventional gasoline vehicles. Treat as an order-of-magnitude estimate. | 0.242 kg / mile | Approximation based on US EPA average vehicle factor | 2024 |
| Electric vehicle efficiency Model year 2025 median EV energy consumption (39 kWh per 100 miles combined). This is an electricity-use factor, not a CO2e factor; it is combined with the electricity grid factor (see electricity.json) to estimate EV emissions per mile. | 0.39 kg / kWh per mile | US DOE/EPA fueleconomy.gov | 2025 |
| Public transit (bus or rail, blended)Rough estimate PLACEHOLDER: the EPA Emission Factors Hub publishes separate per-passenger-mile bus and rail transit factors, but the exact current values could not be confidently extracted for this MVP. 0.15 kg CO2e/mile is a rough order-of-magnitude blend of typical published bus and rail transit intensities and should be replaced with the exact EPA hub figures. | 0.15 kg / mile | US EPA GHG Emission Factors Hub / American Public Transportation Association | 2024 |
Flights
| Factor | Value | Source | Year |
|---|---|---|---|
| Domestic flight DEFRA 2025 domestic flight factor, average passenger, including radiative forcing. Applied to an assumed average domestic round trip distance (see calculations/flights.ts) since users report trips, not distances. | 0.229 kg / passenger-km | UK DEFRA / BEIS Greenhouse Gas Conversion Factors | 2025 |
| Short-haul international flight (under ~3,700 km) DEFRA 2025 short-haul economy-class factor, including radiative forcing. | 0.126 kg / passenger-km | UK DEFRA / BEIS Greenhouse Gas Conversion Factors | 2025 |
| Long-haul international flight (over ~3,700 km) DEFRA 2025 long-haul economy-class factor, including radiative forcing. Used as the default factor for a user-reported 'international trip' since most international travel involves at least one long-haul segment. | 0.117 kg / passenger-km | UK DEFRA / BEIS Greenhouse Gas Conversion Factors | 2025 |
Home energy
| Factor | Value | Source | Year |
|---|---|---|---|
| Electricity (US national average) EPA's national weighted-average electricity emission rate. This is a US-wide average; actual grid intensity varies significantly by state and utility. Used when no other country is selected in the calculator. | 0.394 kg / kWh | US EPA Greenhouse Gas Equivalencies Calculator (eGRID-based national average) | 2022 |
| Natural gas EPA's standard CO2 emission factor for natural gas combustion, converted to a per-therm basis. Not currently varied by country; see /methodology. | 5.3 kg / therm | US EPA Greenhouse Gas Equivalencies Calculator | 2024 |
| Electricity (world average) National-average carbon intensity of electricity generation (all sources, fossil and low-carbon), from Ember's Global Electricity Review. Used as the fallback when a user's country isn't in the supported list. | 0.458 kg / kWh | Ember, Global Electricity Review (via Our World in Data) | 2025 |
| Electricity (United Kingdom) National-average carbon intensity of electricity generation, all sources. Actual intensity varies by region and supplier. | 0.217 kg / kWh | Ember, Global Electricity Review (via Our World in Data) | 2025 |
| Electricity (Germany) National-average carbon intensity of electricity generation, all sources. Actual intensity varies by region and supplier. | 0.33 kg / kWh | Ember, Global Electricity Review (via Our World in Data) | 2025 |
| Electricity (France) National-average carbon intensity of electricity generation, all sources. France's grid is unusually low-carbon due to its large nuclear share. | 0.041 kg / kWh | Ember, Global Electricity Review (via Our World in Data) | 2025 |
| Electricity (Canada) National-average carbon intensity of electricity generation, all sources. Varies a lot by province (hydro- and nuclear-heavy provinces are much lower). | 0.191 kg / kWh | Ember, Global Electricity Review (via Our World in Data) | 2025 |
| Electricity (China) National-average carbon intensity of electricity generation, all sources. Actual intensity varies by province and grid. | 0.525 kg / kWh | Ember, Global Electricity Review (via Our World in Data) | 2025 |
| Electricity (India) National-average carbon intensity of electricity generation, all sources. Actual intensity varies by state and grid. | 0.67 kg / kWh | Ember, Global Electricity Review (via Our World in Data) | 2025 |
| Electricity (Japan) National-average carbon intensity of electricity generation, all sources. | 0.477 kg / kWh | Ember, Global Electricity Review (via Our World in Data) | 2025 |
| Electricity (Australia) National-average carbon intensity of electricity generation, all sources. Varies a lot by state grid. | 0.525 kg / kWh | Ember, Global Electricity Review (via Our World in Data) | 2025 |
| Electricity (Brazil) National-average carbon intensity of electricity generation, all sources. Brazil's grid is unusually low-carbon due to its large hydropower share. | 0.11 kg / kWh | Ember, Global Electricity Review (via Our World in Data) | 2025 |
| Electricity (South Korea) National-average carbon intensity of electricity generation, all sources. | 0.417 kg / kWh | Ember, Global Electricity Review (via Our World in Data) | 2025 |
| Electricity (Mexico) National-average carbon intensity of electricity generation, all sources. | 0.474 kg / kWh | Ember, Global Electricity Review (via Our World in Data) | 2025 |
| Electricity (Spain) National-average carbon intensity of electricity generation, all sources. | 0.154 kg / kWh | Ember, Global Electricity Review (via Our World in Data) | 2025 |
| Electricity (Italy) National-average carbon intensity of electricity generation, all sources. | 0.285 kg / kWh | Ember, Global Electricity Review (via Our World in Data) | 2025 |
| Electricity (South Africa) National-average carbon intensity of electricity generation, all sources. South Africa's grid is coal-heavy, giving it a higher-than-average intensity. | 0.699 kg / kWh | Ember, Global Electricity Review (via Our World in Data) | 2025 |
Food
| Factor | Value | Source | Year |
|---|---|---|---|
| Beef meal OWID reports a global-average footprint of ~60 kg CO2eq per kg of beef (farm to retail, including land-use change). Converted to a per-meal figure assuming a 150 g cooked-meat serving, a commonly used reference serving size. Actual footprints vary widely by production system and portion size. | 9 kg / meal | Our World in Data, based on Poore & Nemecek (2018), Science | 2018 |
| Chicken meal OWID reports a global-average footprint of ~6.1 kg CO2eq per kg of poultry meat. Converted to a per-meal figure assuming a 150 g cooked-meat serving. | 0.92 kg / meal | Our World in Data, based on Poore & Nemecek (2018), Science | 2018 |
| Vegetarian meal Scarborough et al. found self-selected vegetarian diets in the UK produce ~3.81 kg CO2e/day. Divided by an assumed 3 meals/day to estimate a per-meal figure. | 1.27 kg / meal | Scarborough et al. (2014), Climatic Change | 2014 |
| Vegan meal Scarborough et al. found self-selected vegan diets in the UK produce ~2.89 kg CO2e/day. Divided by an assumed 3 meals/day to estimate a per-meal figure. | 0.96 kg / meal | Scarborough et al. (2014), Climatic Change | 2014 |
Shopping
| Factor | Value | Source | Year |
|---|---|---|---|
| Clothing itemRough estimate PLACEHOLDER: per-garment footprints vary enormously by material and item (published studies range from ~2-7 kg CO2e for a cotton t-shirt to well over 20 kg CO2e for heavier garments). 10 kg CO2e/item is a rough blended midpoint across common garment types, not a precise or authoritative figure. Treat shopping estimates as order-of-magnitude only. | 10 kg / item | Blended estimate from published apparel lifecycle-assessment studies (e.g. Mistra Future Fashion) | 2024 |
| Electronics purchaseRough estimate PLACEHOLDER: manufacturing footprints vary widely by device (published estimates: ~55-95 kg CO2e for a smartphone, ~150-330+ kg CO2e for a laptop). 200 kg CO2e/item is a rough blended midpoint representing a generic 'electronics purchase,' not a specific product. Treat as order-of-magnitude only. | 200 kg / item | Blended estimate from published device lifecycle-assessment studies | 2024 |
US state electricity data
State-level output emission rate (Table 3) and generation resource mix (Table 4) from EPA's eGRID2023 dataset. "Fossil" sums coal, oil, gas, and other fossil; "Renewables" sums hydro, biomass, wind, solar, and geothermal. Actual intensity still varies by utility within a state.
| State | kg CO₂e / kWh | Fossil | Nuclear | Renewables |
|---|---|---|---|---|
| Alabama | 0.3239 | 57.9% | 32.9% | 9.3% |
| Alaska | 0.3694 | 71.2% | 0% | 28.8% |
| Arizona | 0.3126 | 58% | 28.2% | 13.8% |
| Arkansas | 0.4529 | 68.7% | 23.7% | 7.7% |
| California | 0.1791 | 44.5% | 8.2% | 47.6% |
| Colorado | 0.4949 | 62.7% | 0% | 37.3% |
| Connecticut | 0.2452 | 62.8% | 33.6% | 3.7% |
| Delaware | 0.3194 | 95.4% | 0% | 4.8% |
| District of Columbia | 0.1792 | 51.9% | 0% | 48.1% |
| Florida | 0.3579 | 81.4% | 11.6% | 6.7% |
| Georgia | 0.3254 | 59.8% | 28.9% | 11.3% |
| Hawaii | 0.6326 | 80.1% | 0% | 19.8% |
| Idaho | 0.1424 | 31.9% | 0% | 67.8% |
| Illinois | 0.2152 | 31.4% | 54.9% | 13.6% |
| Indiana | 0.6647 | 86.8% | 0% | 12.6% |
| Iowa | 0.2876 | 38.3% | 0% | 61.7% |
| Kansas | 0.3326 | 35.5% | 17.6% | 46.9% |
| Kentucky | 0.7924 | 92.7% | 0% | 7.2% |
| Louisiana | 0.3461 | 84% | 12.5% | 3% |
| Maine | 0.1437 | 34% | 0% | 65.2% |
| Maryland | 0.2369 | 48.4% | 41.6% | 9.9% |
| Massachusetts | 0.3765 | 80.4% | 0% | 19.6% |
| Michigan | 0.3617 | 66.7% | 23.2% | 10.2% |
| Minnesota | 0.3413 | 46.9% | 20.8% | 32% |
| Mississippi | 0.3757 | 81.1% | 16.1% | 2.7% |
| Missouri | 0.6598 | 74.6% | 13.8% | 11.7% |
| Montana | 0.4826 | 48.5% | 0% | 50.6% |
| Nebraska | 0.4653 | 49.1% | 17.6% | 33.3% |
| Nevada | 0.292 | 63.2% | 0% | 36.7% |
| New Hampshire | 0.1253 | 26.8% | 56.7% | 16.5% |
| New Jersey | 0.2133 | 52.7% | 44.1% | 3.4% |
| New Mexico | 0.3509 | 55% | 0% | 45% |
| New York | 0.2117 | 48% | 22.3% | 29.7% |
| North Carolina | 0.2841 | 52.2% | 33.5% | 14% |
| North Dakota | 0.5887 | 60.4% | 0% | 39.4% |
| Ohio | 0.4846 | 84.1% | 12.2% | 3.7% |
| Oklahoma | 0.2943 | 56.3% | 0% | 43.6% |
| Oregon | 0.1655 | 37.9% | 0% | 62.1% |
| Pennsylvania | 0.2939 | 65% | 31.9% | 2.9% |
| Rhode Island | 0.381 | 91.9% | 0% | 8.1% |
| South Carolina | 0.2542 | 38.6% | 55.2% | 6.1% |
| South Dakota | 0.1522 | 21.3% | 0% | 78.8% |
| Tennessee | 0.2999 | 39.7% | 48.8% | 11.4% |
| Texas | 0.3498 | 65.1% | 7.5% | 27.3% |
| Utah | 0.6447 | 81.6% | 0% | 18.1% |
| Vermont | 0.0237 | 0.2% | 0% | 99.8% |
| Virginia | 0.2448 | 57.8% | 32.6% | 9.7% |
| Washington | 0.1209 | 23.2% | 8.2% | 68.6% |
| West Virginia | 0.8931 | 93.1% | 0% | 6.9% |
| Wisconsin | 0.5278 | 75% | 15.5% | 9.5% |
| Wyoming | 0.8316 | 77.2% | 0% | 22.5% |
Source: US EPA eGRID2023 (Summary Tables).
Comparison benchmarks
The results page compares your total to two reference points, and translates it into a handful of “put another way” equivalents for scale. These aren't emission factors (nothing is multiplied against your answers) — they're fixed reference numbers.
Per-capita averages
Per capita greenhouse gas emissions including land use, in tonnes CO2e (100-year GWP, AR6 factors). This is a total national average across every sector of the economy (industry, agriculture, government, exports, and more), not just the personal-consumption categories this calculator covers, so it will typically run well above your estimate here even if your lifestyle is average.
| Country | Tonnes CO₂e / person / year | Year |
|---|---|---|
| United States | 17.53 | 2024 |
| United Kingdom | 5.64 | 2024 |
| Germany | 7.8 | 2024 |
| France | 5.08 | 2024 |
| Canada | 20.2 | 2024 |
| China | 9.94 | 2024 |
| India | 2.94 | 2024 |
| Japan | 8.14 | 2024 |
| Australia | 22.83 | 2024 |
| Brazil | 13.23 | 2024 |
| South Korea | 12.19 | 2024 |
| Mexico | 4.86 | 2024 |
| Spain | 5.74 | 2024 |
| Italy | 6 | 2024 |
| South Africa | 8.48 | 2024 |
| World | 6.67 | 2024 |
Source: Jones et al., National contributions to climate change (via Our World in Data).
Tree-seedling equivalence
EPA's weighted-average carbon sequestration rate for an urban tree (coniferous or deciduous) over its first 10 years of growth, converted to CO2. A rough equivalence for scale, not a real offset: actual sequestration varies enormously by species, climate, and age, and a tree takes years to reach this rate.
60 kg CO₂ / tree / year. Source: US EPA Greenhouse Gas Equivalencies Calculator.
Gasoline equivalence
EPA/DOT's standard conversion factor (8,887 g CO2 per gallon of gasoline), based on the fuel's carbon content and assuming complete combustion.
8.887 kg CO₂ / gallon. Source: US EPA Greenhouse Gas Equivalencies Calculator.
Miles-driven equivalence
EPA's per-mile CO2e rate for the average gasoline-powered passenger vehicle: the gasoline factor above divided by the 2022 fleet-average fuel economy (22.8 mpg), adjusted for methane and nitrous oxide.
0.393 kg CO₂e / mile. Source: US EPA Greenhouse Gas Equivalencies Calculator.
Home electricity equivalence
EPA's estimate for the average US home's annual electricity use (12,194 kWh in 2022) at the national average grid emission rate. Uses EPA's own equivalencies-calculator assumptions, which differ slightly from the electricity factor used elsewhere in this app.
4,798 kg CO₂ / home / year. Source: US EPA Greenhouse Gas Equivalencies Calculator.
Electricity generation mix (by country)
The “where your electricity comes from” chart on the results page, for countries other than the US (or when no US state is selected). Display only — not used in any kg CO₂e calculation, which relies on the carbon-intensity factors above instead.
| Country | Fossil | Nuclear | Renewables |
|---|---|---|---|
| United States | 57% | 17.4% | 25.6% |
| United Kingdom | 35.6% | 12.4% | 52% |
| Germany | 40.9% | 0% | 59.1% |
| France | 5.1% | 68.8% | 26.1% |
| Canada | 23% | 13.1% | 63.9% |
| China | 58.3% | 4.6% | 37% |
| India | 73.3% | 2.6% | 24.1% |
| Japan | 67.3% | 9.1% | 23.6% |
| Australia | 61.4% | 0% | 38.6% |
| Brazil | 11.3% | 2.1% | 86.6% |
| South Korea | 60% | 29.6% | 10.4% |
| Mexico | 74.1% | 2.8% | 23.1% |
| Spain | 25.4% | 18.8% | 55.9% |
| Italy | 51.2% | 0% | 48.8% |
| South Africa | 82.2% | 4.2% | 13.6% |
| World | 57.4% | 8.8% | 33.8% |
Source: Ember, Global Electricity Review (via Our World in Data), 2025.