# Fuel Economy Converter (MPG to L/100 km)

URL: https://speedycalculator.com/calculators/conversion/fuel-economy-converter/
Last updated: 2026-10-25

> The fuel economy converter converts L/100 km into miles per gallon (U.S. and UK) and kilometres per litre. Because L/100 km measures consumption and mpg measures distance, the conversion is a reciprocal, not a simple multiplication.

## Inputs

- Consumption (L/100 km)

## Results

- Miles per gallon (US)
- Miles per gallon (UK)
- Kilometres per litre
- Gallons (US) per 100 miles

## Formula

```
mpg (US) = 235.215 ÷ (L/100 km)
mpg (UK) = 282.481 ÷ (L/100 km)
km/L = 100 ÷ (L/100 km)
```

## Explanation

Europe and much of Asia rate cars in litres per 100 km, while the U.S. uses miles per U.S. gallon and the UK miles per imperial gallon.

### How to use the Fuel Economy Converter

- **Consumption**
- Every result field is editable: type into **Miles per gallon (US)** or any other result and **Consumption** plus every other field update to match.

Results update as you type, and every field accepts the units shown in its menu.

### How it works

Each value is the reciprocal of consumption, scaled by the length of a mile and the size of a gallon.

### What each result means

- **Miles per gallon (US)** = 235.214583 ÷ [Consumption]
- **Miles per gallon (UK)** = 282.480936 ÷ [Consumption]
- **Kilometres per litre** = 100 ÷ [Consumption]
- **Gallons (US) per 100 miles** = [Consumption] × 0.42514371

### Example values

How the main result changes when **Consumption** changes and everything else stays at the example values above:

Consumption (L/100 km)Miles per gallon (US) (mpg)3.567.25.2544.8733.68.7526.910.522.41416.8

## Worked example

Inputs — Consumption: 7 L/100 km.

Results — **Miles per gallon (US) = 33.6 mpg**; Miles per gallon (UK) = 40.4 mpg; Kilometres per litre = 14.29 km/L; Gallons (US) per 100 miles = 2.98 gal/100 mi.

## FAQ

**Why is the conversion not linear?**
L/100 km is fuel per distance; mpg is distance per fuel, its inverse.

**Why are UK mpg figures higher?**
An imperial gallon is 20% larger than a U.S. gallon.

**What formula does the Fuel Economy Converter use?**
mpg (US) = 235.215 ÷ (L/100 km).


## Sources

- [NIST Special Publication 811 – Guide for the Use of the International System of Units](https://www.nist.gov/pml/special-publication-811)
- [NIST Handbook 44 Appendix C – General tables of units of measurement](https://www.nist.gov/pml/owm/nist-handbook-44-current-edition)