LESS MATH. MORE MILES.
MPG & gas cost calculator
Calculate your fuel economy in miles per US gallon, estimate how much gas your next drive needs, and find the cost of a road trip.
Calculate your MPG
Enter miles driven and US gallons used after filling your tank.
Enter your values to calculate MPG.
LITERGO / 01Road trip gas cost
Estimate fuel needed and gas cost for your next drive.
Enter your values to estimate your trip.
LITERGO / 02MPG to L/100 km converter
Compare US fuel economy with the metric system. US MPG measures distance per gallon; L/100 km measures fuel consumed over a distance. Higher MPG means better fuel economy, while lower L/100 km means better fuel economy.
Enter an MPG value to convert.
How to calculate miles per gallon
Fill your gas tank, reset the trip odometer, drive normally, then fill the tank again. Divide the miles driven by the US gallons added during the second fill-up. For example, 250 miles divided by 10 US gallons equals 25 MPG.
How to calculate road trip gas cost
Divide trip miles by your vehicle’s MPG to find US gallons needed. Multiply the gallons by the gas price per gallon. For example, a 300-mile trip at 25 MPG requires 12 gallons; at $3.50 per gallon, gas costs $42. This is an estimate, not a live gas-price quote.
US gallons versus Imperial gallons
This calculator uses US liquid gallons, not UK Imperial gallons. One US gallon is approximately 3.78541 liters. To convert US MPG to L/100 km, divide 235.214583 by MPG.
Frequently asked questions
How do I calculate MPG?
Divide miles driven by US gallons used. For example, 300 miles on 12 US gallons equals 25 MPG.
How do I calculate gas cost for a trip?
Divide the trip distance in miles by your MPG, then multiply the gallons required by the gas price per gallon.
What affects gas mileage?
Driving speed, traffic, tire pressure, weather and vehicle load all change MPG. Use several fill-ups for a more reliable average.
Estimates can vary with real-world driving conditions.