US MPG to L/100km Converter
Convert US miles per gallon to litres per 100 km — note the US gallon is smaller than the imperial one. Results update as you type; exact factors shown.
One miles per US gallon is 235.2146 litres per 100 km — see the exact factor, not a rounded rule of thumb.
How the us mpg to l/100km converter works
Fuel economy is an inverse quantity: lower L/100 km is better, higher mpg is better. mpg (US) = 235.215 / (L/100 km) because a US gallon is 3.785 L and a mile 1.609 km; mpg (UK) = 282.481 / (L/100 km) with the 4.546 L imperial gallon. UK mpg figures are therefore always 20% higher than US mpg for the same car.
The UK is metric for most trade and science but keeps miles, pints, stone and mpg (with the imperial gallon) in daily life.
Common fuel economy conversions
| From | To | Units |
|---|---|---|
| 15 mpg (US) | 15.681 L/100 km | miles per US gallon to litres per 100 km |
| 20 mpg (US) | 11.7607 L/100 km | miles per US gallon to litres per 100 km |
| 25 mpg (US) | 9.4086 L/100 km | miles per US gallon to litres per 100 km |
| 30 mpg (US) | 7.8405 L/100 km | miles per US gallon to litres per 100 km |
| 35 mpg (US) | 6.7204 L/100 km | miles per US gallon to litres per 100 km |
| 40 mpg (US) | 5.8804 L/100 km | miles per US gallon to litres per 100 km |
| 45 mpg (US) | 5.227 L/100 km | miles per US gallon to litres per 100 km |
| 50 mpg (US) | 4.7043 L/100 km | miles per US gallon to litres per 100 km |
| 55 mpg (US) | 4.2766 L/100 km | miles per US gallon to litres per 100 km |
| 60 mpg (US) | 3.9202 L/100 km | miles per US gallon to litres per 100 km |
| 70 mpg (US) | 3.3602 L/100 km | miles per US gallon to litres per 100 km |
| 100 mpg (US) | 2.3521 L/100 km | miles per US gallon to litres per 100 km |
Units in this converter and their exact factors
| Unit | Symbol | To L/100 km |
|---|---|---|
| litres per 100 km | L/100 km | x |
| kilometres per litre | km/L | 100÷x |
| miles per imperial gallon | mpg (UK) | 282.480936÷x |
| miles per US gallon | mpg (US) | 235.214583÷x |
FAQFrequently asked questions about fuel economy conversion
Which gallon is this?
The US gallon of 3.785 litres. UK figures use the 4.546 litre imperial gallon and look about 20% better.
What is 30 US mpg in L/100km?
7.84 L/100km.
Why do the scales run opposite ways?
Because one is distance per fuel and the other fuel per distance — they are reciprocals.
What is a good US mpg?
Over 35 mpg is efficient for a petrol car; hybrids reach 50 or more.
Where these figures come from
- BIPM — The International System of Units (SI Brochure, 9th edition) — definitions of the base and derived units.
- NIST Special Publication 811 — Guide for the Use of the International System of Units — the exact conversion factors used here.
- National Physical Laboratory (NPL) — United Kingdom's national measurement authority.
Last checked: September 2026. Conversion factors are fixed by definition and do not change with tax years or regulations.