Methodology
How the calculator turns your answers into tonnes of CO2 equivalent, and where every number comes from. No magic, no proprietary models.
1. Diet
We use per-capita annual diet emissions from Scarborough et al. (2023, Nature Food), based on the EPIC-Oxford cohort. Six diet categories: heavy meat (>100 g/day), medium meat (50-100 g/day), low meat (<50 g/day), pescatarian, vegetarian, vegan.
Values: heavy 3.32, medium 2.42, low 1.88, pescatarian 1.66, vegetarian 1.39, vegan 1.05 tCO2e/yr. These cover food production from farm to retail; they do not include cooking energy (which sits under home electricity).
2. Driving
Per-km factors from UK DEFRA Greenhouse Gas Reporting Conversion Factors 2024:
Petrol/diesel average: 0.171 kg CO2e/km. Hybrid: 0.121. Plug-in hybrid: 0.084.
For electric cars we apply 0.18 kWh/km consumption and multiply by your country's grid carbon intensity, so the same EV in France emits roughly 6x less than in Poland.
3. Flying
Per-passenger-km factors from DEFRA, including a 1.9x multiplier for non-CO2 high-altitude effects (radiative forcing): short 0.158, medium 0.149, long 0.146 kg CO2e/passenger-km.
Typical round-trip distances: short 1500 km, medium 5000 km, long 18000 km. So one long-haul return is roughly 2.6 tCO2 by itself.
4. Home heating + electricity
Heating fuels (DEFRA, kg CO2e/kWh): natural gas 0.183, oil 0.247, district heat 0.140 (EU average), wood/biomass 0.020 (short-cycle).
If your heating is electric, we apply your country's grid intensity instead. Electric resistive heating in France emits ~3 g CO2/kWh of heat; in Poland it emits ~119 g.
Defaults if you skip the kWh fields: 12,000 kWh/yr heating, 3,800 kWh/yr electricity. Both are then divided by household size.
5. Stuff
Lifestyle consumption (clothes, electronics, furniture, services) is grouped into three OECD-style buckets: light 0.6, moderate 1.4, heavy 2.6 tCO2e/yr.
These are rough averages, not granular line items. The big variance in this category is fast fashion and electronics churn.
6. Country comparisons
Per-capita country averages are territorial CO2 (production-based) for 2022 from the Global Carbon Project via Our World in Data. Consumption-based (importing the embodied carbon of imports) values would be a few percent higher for net importers like the UK and a few percent lower for big exporters like China.
Population values are from the World Bank for 2023.
Grid carbon intensity is from IEA Electricity Information for 2023.
7. Percentile estimation
There is no public micro-data on personal carbon footprints by country. We approximate the within-country distribution as log-normal around the country mean, with sigma ~0.55 (calibrated against UK and US household survey distributions).
Treat the percentile as a ranking signal, not a precise statistic. The total tCO2 number is more reliable than the percentile.
Key assumptions and caveats
- Territorial emissions only. Imports' embedded carbon is not added to your country.
- No offsets are subtracted. They live in a separate accounting universe.
- Household energy is split equally between residents.
- The 1.9x flight multiplier reflects current scientific consensus on aviation non-CO2 effects.
- All numbers are estimates. The smallest decimal in this report is more precise than the underlying data.
Sources
- Our World in Data — CO2 emissions — Per-capita and total CO2 by country, 1750-present. CC BY 4.0.
- Global Carbon Project — Source for the OWID country series.
- UK DEFRA Greenhouse Gas Reporting Conversion Factors 2024 — Activity emission factors for transport, fuels, heating. Open Government Licence v3.0.
- Scarborough et al. (2023), Nature Food 4, 565-574 — Per-capita diet emissions by dietary pattern.
- Poore and Nemecek (2018), Science 360, 987-992 — Foundational meta-analysis of food-system emissions.
- IEA Electricity Information — Country-level grid carbon intensity.
- World Bank — Population — Country populations, 2023.
- World Inequality Lab — Climate Inequality Report 2023 — Top 1 / top 10 / bottom 50 global emitter averages.
- IPCC AR6 Working Group III — Per-capita Paris-aligned budget for 1.5C pathway.