Gas Mileage Calculator
Calculate fuel economy in US or UK MPG, L/100 km, or km/L. Estimate trip fuel and cost in your currency, or compare two cars.
Units and currency
Entered values are converted when units change. Changing currency clears the fuel price.
How to Use the Gas Mileage Calculator
The calculator supports US MPG, UK MPG, L/100 km, and km/L. In “Measure Consumption,” enter the distance driven and fuel used; the calculator applies the correct formula for your selected units.
In “Trip: Fuel Needed,” enter the route distance and average fuel economy. Add the price per gallon or liter to see the full trip cost in your selected currency.
In “Compare 2 Cars,” enter two fuel-economy figures over the same distance. The calculator shows the difference in fuel and cost in whichever units you choose.
What the Calculator Works Out
Real Consumption
Real-world fuel economy in US or UK MPG, L/100 km, or km/L based on distance and fuel used.
Trip Estimate
Fuel needed and trip cost using your selected distance, volume units, and currency.
Car Comparison
Fuel and cost differences between two cars over the same distance.
Frequently Asked Questions
How do I measure real fuel consumption?
Fill the tank, reset the trip odometer, drive a meaningful distance, then fill it again. For MPG, divide miles by gallons. For L/100 km, divide liters by kilometers and multiply by 100. The calculator handles either formula.
What counts as normal fuel consumption?
Many gasoline cars return roughly 25–35 MPG (US), while larger SUVs may be closer to 15–25 MPG. Diesel and hybrid vehicles can be higher. Driving conditions, load, weather, and maintenance all affect the real result.
Can I account for traffic?
Yes. Use a city-driving average rather than a highway figure. Stop-and-go traffic increases fuel consumed per distance, so MPG goes down while L/100 km goes up. No separate traffic adjustment is needed.
Why compare two cars?
To see the savings up front, before you buy or replace a car. The calculator shows the difference in fuel and cost over a specific mileage — for example, 20,000 km a year. It helps you judge whether the price gap between an efficient and a thirstier model pays off within a reasonable time.
Does fuel consumption differ between winter and summer?
Yes — in winter it runs 10–25% higher. The reasons: engine warm-up, thicker oil, the heater and defrosters, and loose snow under the tires. For an accurate yearly estimate, calculate two periods separately: summer consumption and winter (add 15–20%), then add them up.