MPG Calculator — Fuel Economy

How fuel economy is measured

Fuel economy tells you how far a vehicle travels on a given amount of fuel. In the United States and the United Kingdom it is expressed in miles per gallon (MPG): the higher the number, the less fuel you use. Most of Europe, Canada and Australia use litres per 100 kilometres (L/100 km), where a lower number is better, and some countries use kilometres per litre. This calculator takes your trip distance and the fuel you put in the tank and shows all of these at once.

US gallons versus UK gallons

The most common source of confusion is that there are two gallons. A US gallon is 3.785 litres and an imperial (UK) gallon is 4.546 litres, so a car that gets 35 MPG on the US scale gets about 42 MPG on the UK scale. When comparing a manufacturer's figure with your own measurements, make sure both use the same gallon. The tool reports both values so you can compare against the label that applies in your country.

Getting an accurate measurement

For a reliable figure, fill the tank until the pump clicks off, reset the trip odometer, drive as you normally would and fill the tank again to the same point. Divide the distance by the fuel added. Doing this over several tanks smooths out differences in driving conditions, temperature and tyre pressure. If you enter the price per gallon or litre, the calculator also shows the cost per mile and per 100 km, which helps when comparing vehicles or budgeting for a long trip.

The converter at the bottom translates a known figure, such as the 30 MPG on a spec sheet, into the other units. To plan a specific journey, try the fuel cost calculator. Everything runs in your browser, and none of your data is uploaded.