How to convert UK mpg to L/100km
L/100km = 282.481 ÷ UK mpg · L/100km = 235.215 ÷ US mpg
For example, 45 mpg is 282.481 ÷ 45 = 6.3 L/100km. Lower L/100km means better economy.
UK mpg to L/100km conversion table
| UK mpg (mpg) | L/100km (L/100km) |
|---|---|
| 20 | 14.1 |
| 25 | 11.3 |
| 30 | 9.4 |
| 35 | 8.1 |
| 40 | 7.1 |
| 45 | 6.3 |
| 50 | 5.6 |
| 55 | 5.1 |
| 60 | 4.7 |
| 65 | 4.3 |
| 70 | 4 |
| 80 | 3.5 |
Why higher mpg means lower L/100km
Miles per gallon measures distance per unit of fuel, so higher is better. Litres per 100 km measures fuel per unit of distance, so lower is better. Because one is the inverse of the other, the conversion is a division rather than a multiplication. The same formula works in both directions.
To measure your own car's economy, use the MPG calculator.
Sources
Rates and rules last checked 15 October 2026. These figures are a guide. For a decision that matters, confirm with the official source.