Gas Mileage Cost Calculator

The formula is gallons = distance / MPG. A 300-mile trip in a car that gets 28 MPG burns 300 / 28 = 10.71 gallons. Multiply by the pump price for fuel cost: 10.71 gallons at $3.50 per gallon is $37.50. Flip the round-trip switch when you also need to drive back; the calculator doubles the distance before running the math (so 300 becomes 600 miles and 21.43 gallons). Vehicle MPG is the single most leveraged input here. Swapping from a 20 MPG SUV to a 35 MPG hybrid for the same 300-mile trip drops fuel cost from $52.50 to $30.00, a 43% saving without changing anything else.

AAA reported a US regular-gas average of $3.89 per gallon on July 15, 2026. That national figure changes daily and can differ materially from the stations on your route. Replace the calculator's editable $3.50 example with a current local or route price before relying on the estimate.

The EPA estimates that burning one US gallon of gasoline releases about 19.6 pounds of CO2 (EPA-420-F-23-014, 'Greenhouse Gas Emissions from a Typical Passenger Vehicle'). The math is just gallons * 19.6, so a 300-mile trip in a 28 MPG car emits 10.71 * 19.6 = 210 pounds of CO2 from the tailpipe. The 19.6 figure already includes the carbon released when the gasoline burns in the engine; it does not include the upstream emissions from extracting, refining, and shipping the fuel (the EPA's well-to-wheels number is closer to 24 pounds per gallon). EVs show zero tailpipe CO2 here. The actual climate impact of an EV depends on how clean your local power grid is, which is highly regional and excluded from this estimate by design.

MPGe (miles per gallon equivalent) is the EPA's apples-to-apples metric for electric and plug-in hybrid vehicles. The conversion factor is 33.7 kWh of electricity = 1 US gallon of gasoline equivalent, picked because both contain about the same energy. A Tesla Model 3 rates around 131 MPGe combined, which means it uses the energy of one gallon of gas to travel 131 miles. At the US average residential electricity price of $0.13 per kWh, that works out to roughly 3.3 cents per mile in electricity, versus about 12.5 cents per mile for a 28 MPG gas car at $3.50/gal. Pick 'Electric (EV)' or 'Hybrid' under vehicle type and the calculator surfaces this context next to your result.

A trip cost is a one-off: distance, gallons, dollars, done. A commute cost is the same math run on a recurring schedule, and the multiplier dominates. Take a 30-mile round-trip commute in a 28 MPG car at $3.50/gal: 30 / 28 * 3.50 = $3.75 per day in fuel. That sounds trivial. Run it across 240 working days a year and you are at $900, before tolls, parking, or wear. Across a 5-year car-ownership cycle that single commute decision is $4,500 in pump receipts. Use the per-day output to extrapolate: multiply the daily figure by the working days you actually expect to drive (most US workers commute 220 to 250 days after PTO and holidays), not by 365.