Carbon Footprint Calculator
Estimate household emissions from driving and energy with disclosed EPA factors. Your work stays on this device whenever possible.
How to use Carbon Footprint Calculator
- Enter distance driven in a gasoline car under Gasoline-car miles; leave it at 0 if you did not drive.
- Fill Electricity used (kWh) from your utility bill and Natural gas burned (therms) from the gas bill.
- Add fuel bought separately, for example for a mower or generator, in Additional gasoline (US gallons).
- Set Period to "Entered period" to keep the totals as typed, or "Monthly values × 12" to scale monthly figures to a year.
- Press "Estimate selected emissions" and read the itemized kilograms of CO₂e for Driving, Electricity, Natural gas and Additional gasoline.
Worked example
Enter 1,000 miles, 500 kWh and 20 therms, leaving gasoline at 0 and Period on "Entered period". Driving = 1,000 × 0.393 = 393.0 kg; Electricity = 500 × 0.6375 = 318.75, shown as 318.8 kg; Natural gas = 20 × 5.306 = 106.12, shown as 106.1 kg. The selected-source total is 817.87, displayed as 817.9 kg CO₂e (0.818 metric tonnes).
When to use this tool
- Comparing a household's monthly driving and utility emissions before and after switching to a heat pump.
- Estimating the yearly impact of a commute by scaling monthly values with the times-12 option.
- Preparing a rough figure for a school sustainability project that only needs a partial estimate.
Important limitations
This is a partial US-average estimate, not a complete personal inventory. Electricity varies substantially by grid region, and the form does not include food, purchases, flights, waste, or upstream supply-chain emissions.
Frequently asked questions
Which emission factors does it use?
The factors are 0.393 kg per mile, 0.6375 kg per kWh, 5.306 kg per therm and 8.89 kg per gallon of gasoline, drawn from US EPA equivalency tables. They are printed under the result so you can verify each line.
Is this my complete carbon footprint?
No. It covers only four sources. Flights, food, goods, waste, heating oil and public transit are not included, so the total is labelled a selected-source figure rather than a full inventory.
Why might my electricity number be wrong?
The kWh factor is a single national average. Grids differ widely, with hydro or nuclear regions emitting far less per kWh than coal-heavy ones, so a location-specific factor from your utility will be more accurate.
What does CO₂e mean in the results?
It stands for carbon dioxide equivalent, meaning other greenhouse gases are converted to the warming effect of CO₂. The tool also gives the total in metric tonnes with three decimals for comparisons.
What happens if I enter a negative value?
The tool rejects it with an error and asks for non-negative activity values, since emissions cannot be negative here. Blank fields are read as zero, so unused sources add nothing.