Unit converter
Fuel economy.
Convert mpg (UK) to L/100 km, or pick any of the 7 units in the menus. Type in either box and the other follows. Economy and consumption run in opposite directions, so converting between them is a division. The US and imperial gallons differ, so mpg does too.
| mpg (UK) | L/100 km |
|---|---|
| 1 mpg (UK) | 282.481 L/100 km |
| 2 mpg (UK) | 141.24 L/100 km |
| 3 mpg (UK) | 94.1603 L/100 km |
| 4 mpg (UK) | 70.6202 L/100 km |
| 5 mpg (UK) | 56.4962 L/100 km |
| 10 mpg (UK) | 28.2481 L/100 km |
| 15 mpg (UK) | 18.8321 L/100 km |
| 20 mpg (UK) | 14.124 L/100 km |
| 25 mpg (UK) | 11.2992 L/100 km |
| 50 mpg (UK) | 5.64962 L/100 km |
| 75 mpg (UK) | 3.76641 L/100 km |
| 100 mpg (UK) | 2.82481 L/100 km |
| 250 mpg (UK) | 1.12992 L/100 km |
| 500 mpg (UK) | 0.564962 L/100 km |
| 1000 mpg (UK) | 0.282481 L/100 km |
- Every unit in the menus is defined against L/100 km, so any pairing converts by the same single route.
Definitions
- Miles per imperial gallon measures economy: higher is better. UK brochures use it, and the imperial gallon is 4.546 09 L.
- Litres per 100 km measures consumption: lower is better. It is the figure EU and UK official documents lead with.
- Fuel economy is reciprocal: more miles per gallon is less fuel per 100 km. A US gallon is smaller than an imperial gallon, so US mpg and UK mpg are different numbers for the same car.
- Every unit in the menus is exact by definition, so the only rounding on this page is the one you choose for the display.
How it works
Every value is converted into litres per 100 km and then back out into the unit you asked for. One route covers every pairing in the menus, so an unusual combination is no less accurate than a common one, and adding a unit affects only that unit.
Both boxes are live. Whichever one you last typed in is the source, changing either menu recalculates straight away, and Swap exchanges the units and the values so the number you are reading stays where you are looking.
Display precision limits significant figures rather than decimal places, which matters here because a reciprocal magnifies rounding: a figure trimmed at one end of the scale moves further at the other. Only the display is rounded. The editable box always holds a plain number at full working precision, so you can carry on from either side.
Common questions this answers: what 40 mpg (UK) is in litres per 100 km (7.06202 L/100 km), what halving it does (14.124 L/100 km, not half of 7.06202), and which way round the units run — a higher mpg (UK) always means a lower L/100 km.
Common conversions
- UK MPG to litres per 100 kilometres
- Litres per 100 kilometres to UK MPG
- US MPG to UK MPG
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