MPG vs L/100km: Which Fuel Economy Metric Is Better?

If you have ever compared cars across countries, you have probably run into two very different ways of describing fuel economy: miles per gallon (MPG) and liters per 100 kilometers (L/100km). They measure the same thing — how much fuel a car uses — but they express it in opposite directions.

How the Two Metrics Differ

MPG measures distance per unit of fuel. A higher number is better, because it means you travel further on each gallon. This is the standard in the United States and, in a slightly different form, the United Kingdom.

L/100km measures fuel per unit of distance. A lower number is better, because it means you burn less fuel to cover the same 100 kilometers. This is the standard across most of Europe, Canada, Australia, and much of the world.

The key insight is that the relationship between them is not linear — it is inverse. As MPG climbs, each additional mile per gallon saves less fuel than the last.

Why Europe Prefers L/100km

L/100km lines up naturally with how people budget fuel. If you know a trip is 300 km and your car uses 7 L/100km, you can immediately calculate that you will need about 21 liters. It also tracks with the metric system used for distance and volume everywhere outside the US, making it intuitive for most of the world.

Why the US Sticks With MPG

MPG has deep cultural roots in the United States and matches the gallon-and-mile units Americans use every day. A “bigger is better” number is also easy to market, which is why window stickers prominently feature MPG figures.

The Conversion Formula

Converting between the two is straightforward:

• MPG to L/100km: divide 235.214 by your MPG. So 30 MPG = 235.214 ÷ 30 ≈ 7.84 L/100km.
• L/100km to MPG: divide 235.214 by your L/100km value.

The constant 235.214 comes from combining the conversions between gallons and liters and between miles and kilometers.

Which Is Better?

Neither is objectively superior — they are two views of the same data. L/100km is arguably more honest about real fuel use, especially when comparing already-efficient cars, while MPG is more familiar to American drivers. The good news is you do not have to choose. Our MPG to L/100km converter translates instantly between both, so you can shop and compare with confidence wherever you are.