Vehicle Emissions Calculator
Calculate your car's annual CO₂ emissions in pounds based on miles driven and vehicle type. Use it to compare the environmental cost of upgrading to a more fuel-efficient car or changing driving habits.
About this calculator
Internal combustion engines emit approximately 19.6 lbs of CO₂ for every gallon of gasoline burned — a figure derived from the carbon content of fuel rather than engine efficiency. This calculator divides your annual miles by the vehicle's assumed fuel economy (SUV: 20 mpg, sedan: 28 mpg, truck: 18 mpg, hybrid: 25 mpg) to find gallons consumed, then multiplies by 19.6. The formula is: CO₂ (lbs) = (annualMiles ÷ mpg) × 19.6. City driving percentage affects real-world fuel economy; most vehicles achieve 15–30% lower mpg in stop-and-go traffic versus highway conditions. Fuel price allows you to calculate annual fuel cost alongside emissions, making it easy to see the financial and environmental payoff of switching vehicles.
How to use
Suppose you drive 12,000 miles per year in an SUV (20 mpg assumed) with fuel at $3.50/gallon. Step 1 — gallons used: 12,000 ÷ 20 = 600 gallons. Step 2 — CO₂ emissions: 600 × 19.6 = 11,760 lbs of CO₂ per year (about 5.3 metric tons). Step 3 — fuel cost: 600 × $3.50 = $2,100/year. Now compare to a sedan (28 mpg): 12,000 ÷ 28 = 429 gallons → 429 × 19.6 = 8,404 lbs CO₂ and $1,500 in fuel — saving over 3,350 lbs of CO₂ and $600 annually just by switching vehicle class.
Frequently asked questions
How many pounds of CO₂ does a car emit per mile driven?
It depends on fuel economy. A sedan averaging 28 mpg emits about 19.6 ÷ 28 ≈ 0.70 lbs of CO₂ per mile, while a truck at 18 mpg emits roughly 1.09 lbs per mile. The 19.6 lbs-per-gallon figure is a physical constant based on the carbon content of gasoline set by the U.S. EPA. Over 12,000 miles, that difference adds up to thousands of pounds of CO₂ annually. Choosing a higher-mpg vehicle is one of the single largest personal emissions reductions available.
Why does city driving increase vehicle carbon emissions compared to highway driving?
Frequent acceleration and braking in city traffic burns more fuel per mile than steady highway cruising, where engines operate near their efficiency sweet spot. Idling at stoplights also consumes fuel while producing zero forward progress. Most vehicles achieve 15–30% worse fuel economy in city conditions versus highway. This calculator uses a blended mpg, so if you drive 80% city miles, your real-world emissions will be higher than the stated highway rating suggests. Hybrids partially recover braking energy, which is why they perform proportionally better in city conditions.
How does my vehicle's CO₂ output compare to the average American car?
The average new passenger car sold in the U.S. emits roughly 4.6 metric tons (about 10,100 lbs) of CO₂ per year, based on EPA data for ~15,000 annual miles. An SUV driven 15,000 miles at 20 mpg produces approximately 14,700 lbs — well above average. A fuel-efficient sedan driven 10,000 miles might emit only 7,000 lbs. Transportation accounts for the largest share of U.S. greenhouse gas emissions (~29%), making vehicle choice one of the most impactful personal climate decisions. Electric vehicles shift emissions to the power grid, often achieving the equivalent of 80–100+ mpg.