⛽ Gas Mileage Calculator
Calculate your vehicle's fuel economy in MPG or L/100km, and optionally estimate fuel cost for a trip.
Trip Details
Your Result
MPG uses US gallons. Enter a fuel price to see cost per distance unit and total trip cost.
How the Gas Mileage Calculator Works
Fuel economy measures how efficiently a vehicle uses fuel. In the US it's typically expressed as miles per gallon (MPG); most other countries use liters per 100 kilometers (L/100km), where a lower number means better efficiency.
Formula
km/L = Kilometers Driven ÷ Liters Used
L/100km = (Liters Used ÷ Kilometers Driven) × 100
Trip Cost = Fuel Used × Price per Unit
Converting Between Units
All inputs are first converted to a common basis (miles and gallons) to calculate US MPG, then converted to liters per 100km and km/L using standard conversion factors (1 mile = 1.60934 km, 1 gallon = 3.78541 liters).
Worked Example
Driving 300 miles on 10 gallons of fuel gives a fuel economy of 300 ÷ 10 = 30.0 MPG. Converting to metric units, that same vehicle covers about 12.75 km per liter, equivalent to 7.84 L/100km.
Frequently Asked Questions
What is a good MPG?
Most modern gasoline cars average 25-35 MPG combined, while hybrids can exceed 50 MPG. Larger trucks and SUVs typically average 15-22 MPG.
Why is a lower L/100km better?
L/100km measures how much fuel is needed to travel a fixed distance, so a lower number means the vehicle uses less fuel to cover the same distance — meaning better efficiency.
How do I calculate my trip's fuel cost?
Enter your fuel price per gallon or liter, and the calculator will multiply it by the fuel used for the trip to estimate total cost, plus the cost per mile or kilometer.