Fuel Cost Calculator
Estimate the fuel cost of a trip from distance, your car's fuel economy and the price of gas, and split it between passengers.
How fuel cost is calculated
Work out how much fuel the trip needs, then multiply by the price per unit of fuel.
Fuel cost = Distance ÷ Fuel economy × Price per gallon
With metric units: fuel used = distance (km) × L/100km ÷ 100, then multiply by the price per liter. The calculator converts between all units for you, so you can mix miles with liters if you need to.
A 300-mile trip in a car that gets 28 mpg uses 300 ÷ 28 = 10.7 gallons. At $3.45 a gallon that costs $36.96, or $73.93 for the round trip.
Fuel economy units explained
- mpg (US): miles per US gallon. Higher is better.
- mpg (UK): miles per imperial gallon, about 20% higher than the US figure for the same car.
- L/100 km: used in Europe, Canada and Australia. Lower is better. To convert, divide 235.2 by US mpg.
- km/L: used in parts of Asia and Latin America. Higher is better.
Ways to cut fuel costs
- Keep tires at the recommended pressure; under-inflation can cost up to 3% in economy.
- Highway economy usually peaks around 50–60 mph (80–95 km/h). Driving at 75 mph can use about 15% more fuel than at 60.
- Remove roof racks and unnecessary weight.
- Use fuel price apps to find cheaper stations along your route.
Frequently asked questions
How do I calculate gas cost for a trip?
Divide the distance by your car's mpg to get gallons needed, then multiply by the price per gallon.
How do I convert mpg to L/100 km?
Divide 235.215 by the US mpg figure. For example, 30 mpg is about 7.8 L/100 km.
Does the calculator include tolls or wear and tear?
No, only fuel. The IRS standard mileage rate is a useful guide if you want to include all vehicle costs.
Last reviewed Oct 20, 2026. Results are estimates; check important decisions with a qualified professional.