Carbon Footprint Calculator
The household year, weighed — the electric meter, the gas meter and the driveway converted to carbon dioxide by EPA factors, in the tons that argue back.
Carbon Footprint Calculator
Results recalculate instantly on every keystroke. Nothing you type is transmitted.
What this result does not account for
- Prices the three metered lines — flights, diet and goods ride outside
- kWh 0 to 10,000; therms 0 to 2,000; miles 0 to 50,000; MPG 5 to 200
In short: 700 kilowatt-hours, 40 therms and 800 miles a month weigh 1,624 pounds of CO2 — 8.8 metric tons over the year, with the drive and the meter trading the biggest line and about 406 mature trees needed to drink it. The average American home's energy lines run near 7.5 tons; this page prices YOURS.
Formula
lb = kWh × 0.86 + therms × 11.7 + gallons × 19.4; tons = lb × 12 ÷ 2,204.6
Carbon is a rate, not a vibe: EPA's national factors price every kilowatt-hour at about 0.86 pounds of CO2, every therm of gas at 11.7, every gallon of gasoline at 19.4. The meters convert directly — the bill already states the kWh and the therms, the odometer and the MPG give the gallons. Grids differ (hydro-heavy regions run under 0.1, coal-heavy over 1.5), so the national factor is a middle-of-the-grid assumption the page states rather than hides. A mature tree drinks about 48 pounds a year, which turns the tonnage into a forest.
Worked Example
- Enter the month's electricity and gas from the bills.
- Enter the miles driven and the car's MPG.
- Read the year in tons, the three lines, and the trees.
Defaults: 700 kWh, 40 therms, 800 miles at 28 MPG — 1,624 lb a month, 8.8 metric tons a year, about 406 trees.
Strengths & Limits Of This Model
Where this engine is strong
- EPA factors applied to YOUR meters
- The biggest line named, not guessed
- The tree count that keeps tons honest
Where it stops
- National grid factor — regional grids run far cleaner or dirtier
Practical Use Cases
Bill reviews
the meters, weighed in carbon
Electrification
what swapping gas for grid does
Offsets
the tree count, honest
Methodology & Editorial Standards
Computation runs in IEEE-754 double precision at full internal precision; rounding to two decimal places occurs strictly at the display layer, so no cumulative drift enters the result. All monetary outputs use accounting presentation — grouped thousands, two decimals, negatives in parentheses — so figures can be transcribed directly into a model or working paper. Division-by-zero and out-of-domain inputs return an em-dash rather than a misleading number.
This engine was reconciled against an independent reference implementation and hand-verified for the worked example above before release. Our full five-stage review process is published on the About Us page.
Disclaimer. This calculator is provided for informational and modelling purposes only and does not constitute financial, tax, legal, medical, or engineering advice. Verify all figures with a qualified professional before acting on them.
Carbon Footprint Calculator — 8 Expert FAQs
8 analyst-written answers to the questions practitioners actually ask — optimised for voice and answer-engine retrieval.
What is a carbon footprint, in pounds?
It is the CO2 your meters imply: EPA's national factors price a kilowatt-hour at about 0.86 lb, a therm of gas at 11.7 lb, a gallon of gasoline at 19.4 lb. Multiply each meter by its factor, add, and the month weighs — the default case weighs 1,624 lb.
Why metric tons?
Because climate accounting is global and metric: 2,204.6 pounds make a metric ton, and household footprints are quoted in them. The average American home's energy lines run near 7.5 tons a year; the default here reads 8.8 with the drive included.
Which line is biggest?
It trades: the drive and the meter fight for it in most households. The lines card names the winner for YOUR numbers — which is the only reduction advice that matters, because the biggest line is the only one worth the first effort.
Doesn't the grid factor vary?
Wildly — hydro-heavy regions run under 0.1 lb per kWh, coal-heavy over 1.5. The page uses the national average of 0.86 and says so; for a regional number, scale the electricity line by your grid's factor from EPA's eGRID.
How many trees offset a household?
A mature tree drinks about 48 pounds of CO2 a year. The default year — 19,491 pounds — takes about 406 trees drinking all year, which is why offsets price in tons and forests are not a substitute for the meter.
What moves the number most?
Order of leverage: the car's gallons (miles and MPG), then heating fuel, then the kilowatt-hours. Electric cars and heat pumps swap gas lines for grid lines — which shrink every year as the grid cleaned from 1.13 lb per kWh in 2015 toward 0.86 today.
Why doesn't this count flights or food?
Because the meters and the odometer are the lines you can read honestly every month. Flights, diet and goods add real tons — full lifestyle calculators chase them — but this page prices what your bills can prove.
Is the footprint per person or per house?
Per house, as billed — the meters do not know how many people live there. Divide the year by heads for a per-person truth; the rent split page's head-count logic applies to carbon exactly as it does to the roof.