Work out what a journey will cost in fuel from the distance, your car's fuel economy and the price per litre. Or enter a distance and the litres you put in to find your mpg.
Results are estimates for planning. Check the figures before you make a financial or health decision.
How the Fuel cost and mpg works
The tool has two modes.
Cost of a trip. Enter the distance in miles or kilometres, your fuel economy and the fuel price per litre. Economy can be UK mpg, US mpg, litres per 100 km or kilometres per litre. Everything is converted to litres per 100 km first:
- UK mpg: litres per 100 km = 282.481 ÷ mpg
- US mpg: litres per 100 km = 235.215 ÷ mpg
- km per litre: litres per 100 km = 100 ÷ km per litre
Litres used = distance in km × litres per 100 km ÷ 100, and cost = litres × price per litre. It also shows cost per mile and per kilometre.
Your mpg. Enter the distance driven and the litres you put in when you filled up. It works out litres per 100 km and converts to UK mpg, US mpg and km per litre.
A UK gallon is 4.54609 litres and a US gallon is 3.78541 litres, so UK and US mpg figures are not the same. Real fuel use varies with speed, load, traffic and weather.
Worked example
Using the default values in the calculator above:
| Input | Value |
|---|---|
| What you want to find | Cost of a trip |
| Distance unit | Miles |
| Distance | 250 |
| Fuel economy unit | Miles per gallon (UK) |
| Fuel economy | 45 |
| Fuel price per litre | £1.45 |
Fuel cost for the trip: £36.62
| Fuel used | 25.3 litres (5.56 UK gallons) |
|---|---|
| Cost per mile | £0.15 |
| Cost per kilometre | £0.09 |
| Distance | 402 km (250 miles) |
Tips and common mistakes
For the most accurate mpg, fill the tank to the same point each time, reset your trip meter, and use the miles driven and litres added at the next fill-up. Do this over a whole tank rather than a short trip.
Use the fuel economy from your own driving rather than the manufacturer’s figure, which is usually better than real use. Check you have picked UK or US mpg, because mixing them up changes the answer by about a fifth. Add tolls and parking separately, as they are not included.
Frequently asked questions
What is the difference between UK and US mpg?
They use different gallons. A UK gallon is 4.54609 litres and a US gallon is 3.78541 litres, so the same car shows a higher number in UK mpg.
What fuel price should I enter?
Use the price per litre you actually pay at the pump. Prices change, so check a recent receipt or your fuel app.
How do I work out my real mpg?
Fill the tank, note the trip distance, then fill again and enter the litres added. Choose the mpg mode in the tool. A full tank’s worth gives the best result.