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Carbon Footprint Calculator | Estimate annual CO2 emissions

Estimates your annual carbon footprint in tonnes of CO2. Enter details about your driving miles, flights, home electricity and gas use, and dietary habits, and the tool applies standard emission factors to each category. The results show where your emissions come from and how you compare with national averages.

Last updated: June 2026 · Free · No sign-up required

Transport

Home & Diet

Results

Enter values above and click Calculate to see your result instantly.

Quick reference

SourceEmission factor
Petrol/gasoline8.89 kg CO₂ per gallon
Grid electricity~0.39 kg CO₂ per kWh (US avg)
Short flight (<3h)~0.5 t CO₂ round trip
Long flight (>3h)~1.6 t CO₂ round trip

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Interpretation guide

Annual footprintHow it compares
< 4 tWell below average (global target zone)
4–10 tBelow US average
~16 tUS national average per person
> 20 tHigh — large reduction opportunity

lightbulb Worked example — a typical driver's footprint

Driving: 12,000 miles/year at 25 MPG → 480 gallons × 8.89 kg CO₂ = 4,267 kg. Home electricity: 10,000 kWh × 0.386 kg/kWh = 3,860 kg. Two short flights ≈ 1,000 kg. Total = 4,267 + 3,860 + 1,000 = 9,127 kg.

Result: ≈ 9.1 tonnes CO₂/year.

What this means: Below the ~14–16 tonne US average but double the global ~4.7 tonne average. The car is the biggest lever: switching to an EV on a clean grid would cut the driving slice by 60–70%.

Formula & methodology

Formula: Total CO₂ = driving + flights + electricity + diet (each converted to tonnes/yr)

How the footprint is added up

Each activity is multiplied by its emission factor, then everything is summed to tonnes of CO₂ per year:

  • Driving: miles ÷ MPG × 8.89 kg CO₂ per gallon of gasoline.
  • Electricity: kWh × grid factor (US average ≈ 0.39 kg/kWh — hydro regions far lower, coal regions higher).
  • Flights and diet use per-trip and dietary-pattern averages.

Factors come from EPA and eGRID publications. The four categories cover roughly 70–80% of a typical personal footprint.

Authoritative source: EPA Greenhouse Gas Calculator

Frequently asked questions

How is a carbon footprint calculated?
The Carbon Footprint Calculator is free, private, and accurate: it runs entirely in your browser (no uploads, no accounts), applies the standard calculation, and explains each step so you can verify the result. Estimates your annual carbon footprint in tonnes of CO2. Enter details about your driving miles, flights, home electricity and gas use, and dietary habits, and the tool applies standard emission factors to each category. The results show where your emissions There is no limit on usage, and it works on any device.
What is the average carbon footprint?
The global average is about 4.7 tonnes of CO₂ per person per year, but it varies enormously: the US average is roughly 14–16 tonnes, Europe 6–8, and many developing countries under 2. The calculator's breakdown — driving, flights, electricity, and diet — lets you see which of your categories are above or below these benchmarks.
How much CO₂ does a gallon of gas produce?
Burning one US gallon of gasoline releases about 8.89 kg (0.0089 tonnes) of CO₂, since the carbon in the fuel combines with oxygen during combustion. Diesel releases slightly more, about 10.2 kg per gallon. The calculator converts your annual miles at your vehicle's efficiency into this per-gallon emission factor.
Does diet really affect my footprint?
Yes — food accounts for roughly 10–30% of a person's carbon footprint, and the type of food matters enormously: a meat-heavy diet can emit nearly twice the greenhouse gases of a vegetarian one, with beef being the largest single contributor due to cattle methane and feed production. The calculator includes diet as one of the four footprint categories.
How can I reduce my carbon footprint?
Enter the required values into the input fields and press the calculate button. The tool applies the formula Total CO₂ = driving + flights + electricity + diet (each converted to tonnes/yr) and returns the result with a short explanation of each step, so you can check the working yourself.
Which emission sources does it include?
Four: driving (miles ÷ MPG × 8.89 kg CO₂ per gallon), flights (per-trip factors by distance), home electricity and gas (kWh and therms × grid and fuel factors), and diet (meat-heavy to plant-based scale). Together these cover roughly 70–80% of a typical personal footprint.
Where do the emission factors come from?
Published government and research sources — e.g. the EPA's 8.89 kg CO₂ per gallon of gasoline and eGRID factors for electricity. Grid factors vary hugely by region: hydro-powered areas can be under 0.1 kg/kWh while coal-heavy grids exceed 0.8.
Is my data sent anywhere when I calculate?
No — the math runs on the page itself, so your lifestyle details never leave your device.
How precise is the estimate?
Good to about ±20–30% — it is an estimate, not an audit. Diet and flights use averages, and your grid's real carbon intensity may differ from the default. It is accurate enough to rank your biggest sources and track changes year over year, which is the point.

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