The formula
How it works
Work out your vehicle’s fuel economy from a distance and the fuel it used. Enter the miles or kilometres driven and the fuel consumed, and the calculator shows the economy in MPG, km/L and L/100 km.
FAQ
How do I measure fuel used accurately?
Fill the tank, reset the trip meter, drive until you need fuel again, then fill up and note the litres or gallons it took. That amount is the fuel used over the trip-meter distance. The more you drive between fills, the more accurate the figure.
What is L/100 km?
It is the metric measure of fuel use — litres burned to travel 100 kilometres — so a lower number is better, the opposite of MPG. The calculator shows both, along with km per litre, so you can read your economy in whichever units you are used to.
What factors affect my car’s gas mileage?
Driving speed and style, tyre pressure, vehicle weight, aerodynamics, terrain, weather, and how well the engine is maintained all influence fuel economy. Aggressive acceleration and idling in traffic tend to lower MPG the most.
How do I calculate the cost of a trip using my gas mileage?
Divide the trip distance by your MPG to get gallons needed, then multiply by the price per gallon. For example, a 300-mile trip at 25 MPG needs 12 gallons, so at $3.50/gallon that trip costs $42.
What is considered good gas mileage for a car?
Most modern gasoline cars average 25–35 MPG combined, while hybrids often exceed 50 MPG. Larger trucks and SUVs typically fall lower, around 15–20 MPG, so “good” depends a lot on the vehicle class.
Why does my gas mileage vary between city and highway driving?
City driving involves frequent stopping, idling and acceleration, which burns more fuel per mile, while steady highway speeds let the engine run more efficiently — though very high speeds increase wind resistance and can lower mileage again.
How do I convert MPG to km/L or vice versa?
Multiply MPG by 0.425 to get km/L, or divide km/L by 0.425 to get MPG, since one US gallon is 3.785 litres and one mile is 1.609 kilometres. The calculator does this conversion for you automatically.
About the gas mileage calculator
This calculator turns a distance and the fuel used into your vehicle’s fuel economy. It reports the result three ways — miles per gallon, kilometres per litre, and litres per 100 kilometres — so it works whatever units you and your car use. Tracking fuel economy is the simplest way to spot a car that needs servicing, compare vehicles, or see the effect of how you drive.
How to use it
Enter the distance you drove and the amount of fuel that distance used, choosing miles-and-gallons or kilometres-and-litres. The calculator shows the economy in all the common units. For example, 300 miles on 12 gallons is 25 MPG; in metric terms that is about 10.6 km/L, or 9.4 L/100 km. Take the readings over a full tank for the most reliable number.
The formula
Miles per gallon is simply distance divided by fuel, ; kilometres per litre is the same idea in metric units. Litres per 100 km inverts that relationship, , which is why a lower figure means better economy. The calculator converts between US gallons, miles, kilometres and litres as needed.
Where it is used
Drivers use it to monitor a car’s efficiency over time, to compare the running cost of different vehicles, and to check whether a claimed economy figure holds up in real driving. A sudden drop in mileage can be an early warning of under-inflated tyres or a mechanical problem. Fleet operators and cost-conscious commuters track it closely because fuel is often the biggest running cost.