About the Carbon Footprint Calculator
This carbon footprint calculator estimates the carbon dioxide your household emits in a year from the four biggest sources most people control: home energy (electricity, natural gas, propane and heating oil), driving, air travel and diet. It adds them up, shows the total in metric tonnes of CO₂ (or CO₂-equivalent for food), and splits the result per person so you can compare with national averages.
Use it to find which part of your life drives most of your emissions before deciding what to change — switching to an EV, adding solar, flying less or eating less meat have very different effects depending on your starting point. Take the numbers straight from your utility bills and odometer for the best estimate.
Fuel factors come from the US EPA GHG Emission Factors Hub (2025 edition, the latest published), and the default grid factor of 0.35 kg CO₂/kWh is the US average from EPA eGRID2023 (about 767–772 lb CO₂/MWh). Change it to match your region or a green-power plan. Flights use 0.16 kg CO₂ per passenger-mile, close to EPA’s long-haul factor. That covers CO₂ only: it leaves out the extra warming from contrails and nitrogen oxides at altitude (radiative forcing), which the UK government estimates by multiplying aviation CO₂ by 1.7, so the flight figure is a conservative estimate. Diet uses published UK per-person averages. Treat the total as a well-informed estimate rather than an audited inventory. It excludes goods, services and waste.
With the default inputs, the household footprint is 15.2 t CO₂e/yr. Change any value above to recalculate instantly.
How to use the carbon footprint calculator
- 1Enter monthly electricity and natural gas use from your utility bills.
- 2Add any propane or heating oil bought in a year.
- 3Enter total household miles driven, the fuel type and fuel economy.
- 4Add up everyone’s flight miles for the year.
- 5Set household size and typical diet, then review the breakdown to see your largest source.
Formula and method
Each activity is multiplied by an emission factor. Electricity uses kWh × your grid factor (about 0.35 kg CO₂/kWh for the US average in EPA eGRID2023). Natural gas uses 5.3 kg per therm, propane 5.72 kg per gallon and heating oil (distillate No. 2) 10.21 kg per gallon, from the EPA GHG Emission Factors Hub. Gasoline cars emit 8.78 kg per gallon burned and diesel 10.21 kg; gallons are miles ÷ mpg. EVs use miles ÷ mi/kWh × the grid factor.
Flights use 0.16 kg CO₂ per passenger-mile, close to EPA’s long-haul factor of 0.163 (medium-haul flights are about 0.129 and flights under 300 miles about 0.207). This counts CO₂ only; including the non-CO₂ warming from contrails and NOx (the UK government suggests a 1.7× multiplier on CO₂) would raise the flight figure by roughly 70%. Diet uses average per-person daily food emissions from a large UK dietary study (standardized to 2,000 kcal a day), from 7.19 kg CO₂e/day for heavy meat eaters to 2.89 kg for vegans, multiplied by 365 and household size. Results are in metric tonnes (1 t = 1,000 kg).
- kWh
- Electricity used per year
- grid factor
- kg CO₂ emitted per kWh generated in your region
- mpg
- Vehicle fuel economy in miles per gallon
- t
- Metric tonnes (1,000 kg)
Worked examples
Two-person home with a gas car
Electricity (10,200 kWh × 0.35) adds 3.57 t and gas (480 therms × 5.3) adds 2.54 t, so home energy is 6.11 t. Driving 12,000 miles at 25 mpg burns 480 gallons × 8.78 kg, or 4.21 t. Flights add 0.8 t (5,000 mi × 0.16 kg) and two average diets 4.11 t (5.63 kg × 365 × 2), for about 15.2 t in total — 7.6 t per person.
Same home with an EV and vegetarian diet
An EV covering 12,000 miles at 3.5 mi/kWh needs about 3,429 kWh, or 1.2 t on the average grid (0.35 kg/kWh) — less than a third of the gas car. Two vegetarian diets drop food to 2.78 t, bringing the household to about 10.9 t.
Single person, oil heat, frequent flyer
Electricity (7,200 kWh × 0.35) adds 2.52 t and 700 gallons of heating oil 7.15 t, so home energy is 9.67 t. Driving 250 gallons adds 2.2 t, 30,000 flight miles 4.8 t (CO₂ only) and a heavy-meat diet 2.62 t — about 19.3 t for one person.
Frequently asked questions
What is a carbon footprint?+
A carbon footprint is the total greenhouse gas emissions caused by your activities, usually expressed in tonnes of CO₂ or CO₂-equivalent (CO₂e) per year. CO₂e converts other gases such as methane into the amount of CO₂ with the same warming effect.
What is the average carbon footprint per person?+
Average footprints differ widely by country. Territorial CO₂ emissions are roughly 14–15 tonnes per person in the US, around 5–7 tonnes in many European countries and about 4–5 tonnes globally. Consumption-based totals that include imported goods are higher.
How can I reduce my carbon footprint the most?+
The biggest levers are usually driving less or switching to an EV, flying less, heating with a heat pump instead of oil or propane, buying renewable electricity or installing solar, and eating less red meat. The breakdown shows which applies most to you.
Why does my electricity grid factor matter?+
The same kWh can emit very different amounts depending on how it is generated. In EPA eGRID2023, US subregions range from about 0.11 kg CO₂/kWh (upstate New York) to about 0.6–0.7 kg (the upper Midwest, Hawaii and Puerto Rico). Enter your local factor, or 0 if you buy certified 100% renewable power.
Does this include everything I buy?+
No. It covers home energy, personal driving, flights and food, which are typically the largest direct sources. Emissions embedded in clothing, electronics, furniture and services are excluded, so a full consumption footprint would be higher.