Carbon Footprint Calculator

Personal annual CO2 from transport, home, food, and goods.

About this calculator

This calculator sums four everyday emission sources into one annual CO2-equivalent total, each using a published per-unit factor rather than one lump average. Driving is priced per kilometre by fuel type (petrol, diesel, hybrid, and EV each carry a different kg-CO2/km factor, with the EV figure already accounting for grid electricity), while air travel adds a 1.9x radiative-forcing multiplier on top of the raw fuel-burn estimate to reflect the extra warming effect of high-altitude emissions like contrails — a widely used but still-debated adjustment. Home energy is split into grid electricity (a 0.42 kg CO2/kWh US-average factor drawn from the EPA's GHG Emission Factors Hub) and natural gas heating, and diet is handled as a fixed annual figure per dietary pattern drawn from Poore & Nemecek's widely-cited 2018 Science meta-analysis of global food-production emissions (a review of roughly 38,000 commercial farms across 119 countries) rather than tallied meal by meal.

Consumer spending on goods and services is converted using a rough dollar-to-CO2 factor from environmentally-extended input-output modeling — the least precise piece of the total, since actual carbon intensity per dollar spent varies hugely by what's actually purchased. The total is benchmarked against global (4.7 t) and US (14.7 t) average footprints and translated into an equivalent number of mature trees needed to absorb it annually. The most common mixup: the electricity factor is a fixed US grid average baked into the formula, so results will run high for anyone on a cleaner grid (hydro, nuclear, renewables-heavy) and low for anyone on a coal-heavy one, since there's no input here to adjust it.

Inputs

Car km/week

Fuel Type

Flights per year

Avg flight hours (one-way)

Electricity (kWh/month)

Natural gas (m³/month)

Diet

Goods & services ($/month)

Tab to move between fields

Results

Total CO2 (tonnes/year)

17.13

Transport (tonnes)4.74

Home energy (tonnes)5.69

Food (tonnes)2.5

Goods & services (tonnes)4.2

% of world average365%

% of US average117%

Trees to offset779

Figures current as of 2025. Sources: U.S. Environmental Protection Agency, GHG Emission Factors Hub (2025 annual update)., Poore, J., Nemecek, T. Reducing food's environmental impacts through producers and consumers. Science. 2018;360(6392):987-992.

How to Use This Calculator

Enter your weekly car driving distance in km and select fuel type.
Set number of round-trip flights per year and average flight hours.
Enter monthly electricity (kWh) and natural gas (m³) usage, and select dietary pattern.
Review Total CO₂ (tonnes/year) and breakdown by transport, home energy, diet, and goods.
Identify your largest emission source and explore reduction strategies for that category first.

How the result changes with Electricity (kWh/month)

Electricity (kWh/month)	Total CO2 (tonnes/year)
450	14.86
675	16
1,350	19.4
2,250	23.94

What each input means

Car km/week: Average kilometres driven per week.
Fuel Type: Select vehicle fuel type
Flights per year: Number of round-trip flights per year.
Avg flight hours (one-way): Average duration of a one-way flight in hours.
Electricity (kWh/month): Monthly household electricity consumption in kWh.
Natural gas (m³/month): Monthly natural gas usage in cubic metres.
Diet: Select dietary pattern
Goods & services ($/month): Monthly spending on consumer goods and services.

What each result means

Total CO2 (tonnes/year): Total annual carbon footprint in metric tonnes CO2e.
Transport (tonnes): Annual CO2 from car and air travel.
Home energy (tonnes): Annual CO2 from electricity and natural gas.
Food (tonnes): Annual CO2e from diet based on Poore & Nemecek (2018).
Goods & services (tonnes): Annual CO2 from consumer spending (EIO-LCA model).
% of world average: Your footprint as a percentage of the global average (4.7 t).
% of US average: Your footprint as a percentage of the US average (14.7 t).
Trees to offset: Approximate mature trees needed to absorb your annual CO2 (22 kg/tree/year).

How this is calculated

Worked example, using the default values

Identify Input Parameters
4 parameters
Car km/week = 150, Fuel Type = 0, Flights per year = 2, Avg flight hours (one-way) = 4 = 8 input(s) provided
Calculate Total CO2
Total CO2 = transportTotal + homeTotal + foodTotal + goodsTotal
17.13 = 17.13
Calculate Transport
Transport = transportCarAnnual + transportFlightAnnual
4.74 = 4.74
Calculate Home energy
Home energy = electricityAnnual + gasAnnual
5.69 = 5.69

Figures and sources

US grid electricity and transport CO2 emission factors (2025) — U.S. Environmental Protection Agency, GHG Emission Factors Hub (2025 annual update).
Per-diet-pattern greenhouse gas emission factors (2018) — Poore, J., Nemecek, T. Reducing food's environmental impacts through producers and consumers. Science. 2018;360(6392):987-992.

Engine last updated September 3, 2026. Checked against 1 independently-derived test — how we verify calculators. Built by Paul Gunder, a software engineer, not a licensed financial, medical, or legal professional.

Frequently Asked Questions

Why does flying add so much more per hour than driving?

Flight emissions use 0.255 kg CO2 per passenger-km at roughly 800 km/h cruising speed, then multiply the result by 1.9 to account for the extra warming effect of high-altitude emissions (contrails and NOx effects beyond the raw CO2). A single 4-hour flight covers roughly 3,200 km, so that one trip alone can add close to the same CO2 as weeks of typical commuting, even before the radiative-forcing multiplier is applied.

How is diet emissions calculated if I don't log individual meals?

The calculator uses a single fixed annual tonnage per dietary pattern — 3.3 t for heavy meat down to 1.0 t for vegan — drawn from Poore & Nemecek, "Reducing food's environmental impacts through producers and consumers," Science, 2018 (360(6392):987-992), a meta-analysis spanning roughly 38,000 farms across 119 countries. It's a category-level estimate rather than a meal-by-meal tally, so switching the diet dropdown changes your food emissions instantly without needing any details about portion sizes or specific foods.

Why would my results look wrong if I'm on a very clean electricity grid?

The home-energy calculation multiplies your kWh usage by a fixed 0.42 kg CO2/kWh factor drawn from the EPA's GHG Emission Factors Hub, which represents the US average grid mix. There's no input to adjust that factor, so anyone on a grid that's heavily hydro, nuclear, or renewables-based will see their home-energy emissions overstated, while anyone on a coal-heavy grid will see them understated relative to their actual local emissions.

What's the least reliable part of the total footprint?

The goods & services component, which converts monthly spending directly into tonnes of CO2 using a flat $0.0007-per-dollar factor drawn from environmentally-extended input-output (EIO-LCA) modeling. Actual carbon intensity per dollar varies enormously by what's purchased — a dollar spent on plane tickets or steel is far more carbon-intensive than a dollar spent on a haircut — so this piece is a rough average, not a category-aware estimate.

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