US MPG to L/100km Converter
Convert US miles per gallon to liters 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 liters 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 US uses customary units (US gallon, short ton, °F) in daily life; NIST SP 811 gives the exact SI factors.
Common fuel economy conversions
| From | To | Units |
|---|---|---|
| 15 mpg (US) | 15.681 L/100 km | miles per US gallon to liters per 100 km |
| 20 mpg (US) | 11.7607 L/100 km | miles per US gallon to liters per 100 km |
| 25 mpg (US) | 9.4086 L/100 km | miles per US gallon to liters per 100 km |
| 30 mpg (US) | 7.8405 L/100 km | miles per US gallon to liters per 100 km |
| 35 mpg (US) | 6.7204 L/100 km | miles per US gallon to liters per 100 km |
| 40 mpg (US) | 5.8804 L/100 km | miles per US gallon to liters per 100 km |
| 45 mpg (US) | 5.227 L/100 km | miles per US gallon to liters per 100 km |
| 50 mpg (US) | 4.7043 L/100 km | miles per US gallon to liters per 100 km |
| 55 mpg (US) | 4.2766 L/100 km | miles per US gallon to liters per 100 km |
| 60 mpg (US) | 3.9202 L/100 km | miles per US gallon to liters per 100 km |
| 70 mpg (US) | 3.3602 L/100 km | miles per US gallon to liters per 100 km |
| 100 mpg (US) | 2.3521 L/100 km | miles per US gallon to liters per 100 km |
Units in this converter and their exact factors
| Unit | Symbol | To L/100 km |
|---|---|---|
| liters per 100 km | L/100 km | x |
| kilometers per liter | 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 liters. UK figures use the 4.546 liter 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 Institute of Standards and Technology (NIST) — United States's national measurement authority.
Last checked: September 2026. Conversion factors are fixed by definition and do not change with tax years or regulations.