How to use
- Enter the fuel economy and choose its unit.
- Enter the trip distance in kilometres and the fuel price per litre.
- Read the economy in all four units and the fuel and cost for the trip.
Options explained
- MPG (US and UK)
- Miles per gallon; higher is better. A US gallon is about 3.785 litres and a UK gallon 4.546, so the same car shows a higher UK mpg.
- L/100 km
- Litres used per 100 km; lower is better. Used in most of the world outside the US and UK.
Conversions
| L/100 km | km/L | mpg (US) | mpg (UK) |
|---|---|---|---|
| 5.0 | 20.00 | 47.0 | 56.5 |
| 7.5 | 13.33 | 31.4 | 37.7 |
| 10.0 | 10.00 | 23.5 | 28.2 |
Fuel economy conversion table
| L/100 km | km/L | mpg (US) | mpg (UK) |
|---|---|---|---|
| 4 | 25.0 | 58.8 | 70.6 |
| 5 | 20.0 | 47.0 | 56.5 |
| 6 | 16.7 | 39.2 | 47.1 |
| 7 | 14.3 | 33.6 | 40.4 |
| 8 | 12.5 | 29.4 | 35.3 |
| 10 | 10.0 | 23.5 | 28.2 |
| 12 | 8.3 | 19.6 | 23.5 |
| 15 | 6.7 | 15.7 | 18.8 |
Lower is better for L/100 km; higher is better for km/L and mpg. A UK gallon (4.546 L) is bigger than a US gallon (3.785 L), so the same car shows a higher mpg figure in the UK.
Trip cost examples
Road trip in Europe. 500 km at 7.5 L/100 km uses 37.5 litres; at €1.60 a litre that is €60.00.
UK motorway drive. 200 miles is 321.9 km. A car doing 45 mpg (UK) uses 20.2 litres; at £1.45 a litre that is £29.30.
US drive in miles and gallons. The trip cost uses kilometres and the price per litre. For 300 miles at 30 mpg (US) and $3.50 a gallon, enter 482.8 km and $0.925 per litre: you need about 37.9 litres (10 gallons), costing $35.00.
Frequently asked questions
What is 30 mpg in L/100 km?
30 US mpg is about 7.84 L/100 km; 30 UK mpg is about 9.42 L/100 km.
Why is my real fuel economy worse than the official figure?
Official figures come from standard test cycles. Traffic, air conditioning, motorway speeds and load all raise real consumption.
Can I use miles and gallons for the trip?
Convert first — one mile is 1.609 km and one US gallon 3.785 litres.
Privacy
This tool runs entirely in your browser. Your files and text are processed on your device and are never uploaded to our servers.