Understanding fuel economy units
US and imperial gallons have different volumes. US mpg uses 3.785411784 L per gallon; imperial mpg uses 4.54609 L. L/100 km measures consumption, so lower is better, while higher mpg means greater distance per fuel. Inputs must be positive.
Conversion method
Fuel use per distance and distance per fuel are reciprocal: US mpg = 235.214583 / (L/100 km). Doubling mpg halves liters consumed over a fixed distance. Other units are converted through L/100 km.
| Unit | 1 unit in base units | Definition |
|---|---|---|
| Liters per 100 km (L/100 km) | 1 | Reciprocal conversion; not a constant factor |
| Miles per gallon (US) (mpg) | 235.214583 | Reciprocal conversion; not a constant factor |
| Miles per gallon (imperial) (mpg (imp)) | 282.480936 | Reciprocal conversion; not a constant factor |
| Kilometers per liter (km/L) | 100 | Reciprocal conversion; not a constant factor |
Worked example and common conversions
10 mpg = 23.5214583 L/100 km. Do not multiply by the conversion for 1: reciprocal conversions require dividing by the actual input.
| From | To |
|---|---|
| 10 mpg | 23.5214583 L/100 km |
| 10 L/100 km | 23.5214583 mpg |
| 10 mpg | 4.2514370803 km/L |
| 10 mpg | 12.009499258 mpg (imp) |