Fuel Cost Formula
In US units, fuel needed = distance ÷ MPG. In metric units, fuel needed = distance × L/100 km ÷ 100. Multiply fuel needed by the price per gallon or liter to get the trip cost.
Compare Real Driving Scenarios
Use one-way distance for the trip result, then check the automatically doubled round-trip cost. The commute estimate separately applies your work days per month, making it easier to compare remote-work schedules, routes, or vehicles.
Tip: Use your vehicle's recent average efficiency—not its advertised rating—and include a buffer for traffic, weather, idling, and detours.
Calculation Example
A 500-mile trip in a 30 MPG vehicle uses about 16.67 gallons. At $3.50 per gallon, the one-way cost is $58.33 and the round trip is $116.67.
Frequently Asked Questions
How do you calculate fuel cost for a trip?
Divide distance by MPG, then multiply by gas price. 500 mi ÷ 30 MPG × $3.50 = $58.33.
What is good gas mileage?
30+ MPG is good for gas cars, 40+ MPG is excellent. Hybrids get 45-60 MPG.
How do I convert MPG to L/100km?
L/100km = 235.215 ÷ MPG. So 30 MPG = 7.84 L/100km.
Does driving faster use more gas?
Yes. Each 5 mph over 50 is like paying $0.20-0.30 more per gallon, per the DOE.