Online Tool Store
Fuel Economy Converter
Convert fuel economy between US MPG, UK MPG, L/100km, and km/L instantly, with every unit shown at once, in your browser.
🔒 This tool runs entirely in your browser. Your files are never uploaded to a server.
Example shown — replace it with your own value and unit.
MPG (US)
MPG (UK)
L/100km
km/L
How the fuel economy converter works
- Enter a fuel economy value and select which unit it's in.
- The tool converts it into US MPG, UK MPG, L/100km, and km/L all at once.
- Every card updates instantly as you type or change the source unit.
The method
Kilometers per liter (km/L) is used as the common base unit. Your input is first converted to km/L, then from km/L into every other unit using each unit's own conversion factor — for MPG that means converting miles to kilometers and gallons to liters; for L/100km, it's simply the reciprocal scaled by 100.
FAQ
Why is US MPG different from UK MPG for the same car?
A US gallon (3.785 liters) is smaller than a UK/imperial gallon (4.546 liters), so the same fuel efficiency produces a higher MPG number under the UK definition — a car rated "30 MPG" in the US would show a noticeably higher number if measured in UK gallons.
Why does L/100km work backward from MPG?
MPG measures distance per unit of fuel (more is better), while L/100km measures fuel per unit of distance (less is better) — that's why the relationship between them isn't a simple straight-line conversion, and why doubling your MPG doesn't just halve your L/100km in a simple way either, except approximately at the same reference point.
What is km/L used for?
It's a straightforward "distance per fuel" measure, similar in spirit to MPG but in metric units — common in regions that use liters and kilometers but still prefer a "distance per fuel unit" framing over L/100km.
Is my input sent anywhere?
No. Every conversion happens instantly in your browser as you type — nothing is sent to Online Tool Store or any other server.
How we compare
| Feature | Online Tool Store | UnitConverters.net | Google unit conversion |
|---|---|---|---|
| Shows all four units at once | ✓ | One pair at a time | One pair at a time |
| Distinguishes US and UK gallons | ✓ | ✓ | Easy to miss |
| No ads | ✓ | Ad-supported | ✓ |
For a quick side-by-side view across every common fuel economy unit, the Online Tool Store Fuel Economy Converter shows every conversion at once.