Carbon Footprint Calculator
Free carbon footprint calculator estimates your annual CO2e from electricity, gas, driving and flights using standard EPA emission factors, with a full breakdown.
Updated 2026-06-14 · Free · No sign-up · Runs privately in your browser
| Source | kg CO₂e / year | Share |
|---|
Show the formula & emission factors
How the Carbon Footprint Calculator Works
This calculator estimates your annual carbon footprint in tonnes of CO2-equivalent (CO2e) from the four largest personal sources: home electricity, natural gas, car driving and flights. Enter your typical usage and it returns your total plus a percentage breakdown so you can see where to focus.
The Formula
Each input is multiplied by a standard emission factor and scaled to a full year:
Annual CO2e = (kWh/mo × 12 × 0.39) + (therms/mo × 12 × 5.3) + (miles/wk × 52 × 0.404) + (flight hrs/yr × 90)
The emission factors used are widely cited EPA/DEFRA values:
- Electricity: 0.39 kg CO2e per kWh (US grid average)
- Natural gas: 5.3 kg CO2e per therm
- Car: 0.404 kg CO2e per mile (average passenger vehicle)
- Flights: ~90 kg CO2e per flight-hour
The result is divided by 1,000 to express the answer in tonnes and compared to the global average of about 4.7 tonnes per person.
Worked Example
A household profile of 900 kWh/month, 50 therms/month, 150 miles/week driving, and 10 flight-hours/year:
- Electricity = 900 × 12 × 0.39 = 4,212 kg
- Natural gas = 50 × 12 × 5.3 = 3,180 kg
- Car = 150 × 52 × 0.404 = 3,151 kg
- Flights = 10 × 90 = 900 kg
- Total = 11,443 kg ≈ 11.4 tonnes CO2e/year (about 2.4× the world average)
Where Emissions Come From
| Source | This example (kg/yr) | Typical share |
|---|---|---|
| Electricity | 4,212 | Largest in many homes |
| Natural gas | 3,180 | Heating-dependent |
| Car driving | 3,151 | Mileage-dependent |
| Flights | 900 | Spikes with long trips |
Cutting Your Footprint
- Target your biggest slice first — the breakdown table shows where the quickest wins are.
- Switch to renewable electricity to slash the per-kWh factor toward zero.
- Combine trips, carpool, or go electric to lower transport emissions.
- Fly less, and direct — fewer take-offs and layovers cut the most per journey.
Frequently asked questions
How is a carbon footprint calculated?+
You multiply each activity by its emission factor — the kilograms of CO2-equivalent it produces per unit — then add them up. This tool uses standard factors: about 0.39 kg per kWh of grid electricity, 5.3 kg per therm of natural gas, 0.404 kg per mile driven, and roughly 90 kg per hour of flying.
What is CO2e?+
CO2e, or carbon dioxide equivalent, is a common unit that converts all greenhouse gases (methane, nitrous oxide and others) into the amount of CO2 that would cause the same warming. It lets you add up different emission sources on one scale.
What is an average carbon footprint?+
The global average is about 4.7 tonnes of CO2e per person per year, but it varies hugely by country. The US averages around 14-16 tonnes per person, while many lower-income nations are under 1 tonne. This calculator covers major personal energy and travel sources, not embedded emissions in goods and food.
Why are flights such a big part of a footprint?+
Flying is energy-intensive per hour, and high-altitude emissions have an extra warming effect. A single long-haul round trip can add a tonne or more of CO2e, often rivaling months of home electricity, which is why frequent flyers tend to have outsized footprints.
How can I reduce my carbon footprint?+
The biggest levers are usually flying less, driving less or switching to an EV, switching to a renewable electricity plan, improving home insulation, and heating efficiently. Use the breakdown to target your largest source first, since that delivers the most reduction per effort.