Free car CO₂ emissions calculator. Estimate your gas or diesel vehicle's annual tailpipe emissions from fuel economy and distance using EPA factors.
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How much CO₂ does your car actually emit? Transportation is one of the largest sources of household greenhouse gases, and a combustion car's emissions come straight from the fuel it burns. This calculator turns your gas or diesel vehicle's fuel economy and annual distance into precise tailpipe CO₂ — per mile, per kilometer, and per year — using official EPA emission factors, then shows how you compare to an average car, an efficient hybrid, and a typical EV.
Tailpipe (or tank-to-wheel) emissions are the CO₂ released when your engine burns fuel. Because carbon in the fuel combines with oxygen from the air, burning one gallon of gasoline releases about 8.89 kg of CO₂, and one gallon of diesel about 10.18 kg. Divide that by your fuel economy and you get grams of CO₂ per mile: a 25 MPG car emits ~355 g/mi, while the US-average car is about 404 g/mi. This tool reports tailpipe CO₂ and also a well-to-wheel figure that adds the ~20–25% of emissions from producing and delivering the fuel. An electric car has no tailpipe CO₂ — its emissions depend on the power grid, which is why EVs belong in the EV Emissions Calculator.
Tailpipe Emissions Formula
Shoppers comparing the CO₂ of gas and diesel models before deciding what to buy.
People tracking their carbon footprint and testing how driving less or better cuts emissions.
Businesses estimating vehicle emissions for sustainability and ESG reporting.
Anyone learning how fuel economy translates into real greenhouse-gas numbers.
Driving is often the largest slice of a household's carbon footprint — know exactly how many kilograms you emit each year.
See how your current MPG stacks up against an efficient hybrid or a typical EV before your next car purchase.
Fuel economy drives emissions directly — watch how a few MPG change both your CO₂ and your fuel bill.
Estimate the number of trees needed to absorb a year of your tailpipe emissions.
Divide the fuel's CO₂ factor by your MPG. A 25 MPG gasoline car emits about 355 g/mi (8,887 ÷ 25), a 35 MPG compact about 254 g/mi, and a 16 MPG pickup about 555 g/mi. The US-average car is roughly 404 g CO₂ per mile.
Tailpipe (tank-to-wheel) counts only the CO₂ from burning fuel in your engine. Well-to-wheel also includes extracting, refining, and delivering that fuel, which adds roughly 20–25% for gasoline and about 20% for diesel. We show the tailpipe figure as the headline and the well-to-wheel estimate separately.
Per gallon, yes — diesel releases about 10.18 kg of CO₂ versus 8.89 kg for gasoline because it is denser. But diesel engines are usually more fuel-efficient, so CO₂ per mile can be similar or lower. This calculator uses the correct per-gallon factor for whichever fuel you pick.
A mature tree absorbs about 21.8 kg of CO₂ per year. A 28 MPG car driven 12,000 miles emits roughly 3,800 kg, needing about 175 trees to offset a single year of driving.
No — an EV has no tailpipe CO₂, so its emissions depend entirely on the electricity grid you charge from. Use our EV Emissions Calculator for grid-based CO₂, an EV-vs-gas comparison, and the manufacturing break-even point. This tool is for gasoline and diesel vehicles.
EPA tailpipe factors: 8,887 g CO₂ per gallon of gasoline and 10,180 g per gallon of diesel. The US-average benchmark of 404 g/mi is reconciled with our Carbon Footprint Calculator so the figures stay consistent across the site.