Carbon Footprint Calculator

Across this calculator's declared input ranges, electricity usage swings your Annual CO2 total more than driving, natural gas, or flights individually do -- a reflection of how carbon-intensive electricity generation still is across much of the US grid on average. If you want to see how switching to a lower-carbon electricity source would change your footprint, try lowering Monthly Electricity and watching the Electricity slice of the breakdown shrink.

Vehicle MPG is purely a fuel-efficiency multiplier applied to Miles Driven / Year to estimate gallons of gasoline burned -- it has no relationship to your home's electricity or natural gas usage. Each of the four emission sources (driving, electricity, natural gas, flights) is calculated independently from its own inputs and then summed into your total.

The driving and heating factors (19.6 lbs CO2/gallon of gasoline, 11.7 lbs CO2/therm of natural gas) come directly from the EPA's own Greenhouse Gas Equivalencies Calculator reference page (8,887 grams CO2 per gallon of gasoline, and 0.0053 metric tons CO2 per therm of natural gas). The electricity factor (about 0.92 lbs CO2/kWh) is a national grid average, but actual carbon intensity varies substantially by region and utility -- a household on a coal-heavy grid emits meaningfully more per kWh than one on a grid with more hydro, nuclear, or renewables, so treat this as a national approximation rather than your utility's specific figure.

It divides your Annual CO2 total by an approximate figure for how much carbon dioxide a tree can sequester in a year, giving a rough sense of how many trees' worth of annual growth would be needed to offset your footprint. Actual sequestration varies widely by tree species, age, and climate, so treat this as an illustrative comparison rather than a literal offsetting plan -- tree planting alone is also a slow, multi-decade process relative to a single year's emissions.

This calculator uses a flat estimate of roughly 1,100 lbs of CO2 per round trip, regardless of whether that trip is a short domestic hop or a long international flight -- real flight emissions vary substantially with distance, cabin class, and aircraft type. If you fly mostly short domestic routes, this flat estimate likely overstates your flight emissions; if you fly mostly long-haul international routes, it likely understates them.