⛽ Fuel Efficiency Converter

This free fuel efficiency converter instantly translates a single fuel economy figure into MPG (US), MPG (UK/Imperial), liters per 100 kilometers (L/100km), and kilometers per liter (km/L) — the four measures used across North America, the United Kingdom, and most of the rest of the world. Enter one value in whichever unit you have, and every other figure updates immediately, making it easy to compare a car's specs no matter which country's convention they were originally published in.

What This Fuel Efficiency Converter Computes

Type a fuel economy number and choose its starting unit — MPG (US), MPG (UK/Imperial), L/100km, or km/L — and the calculator converts it to the other three simultaneously. Behind the scenes, every conversion routes through liters per 100km as a common reference point, so the four numbers you see are always mathematically consistent with one another rather than independently rounded approximations.

Who Should Use This Calculator

This tool is built for anyone comparing vehicles listed in different fuel economy units: US car shoppers researching European or Japanese import models, UK drivers cross-checking a US-spec vehicle's window sticker, rental car customers abroad trying to estimate a foreign car's real running cost, and automotive writers, fleet managers, and students who regularly need to translate between mpg-based and metric fuel economy figures.

Why Unit Conversion Matters Here

Fuel economy isn't reported the same way everywhere. The US uses miles per US gallon, the UK traditionally used miles per Imperial gallon, and most of Europe, Asia, and Latin America use liters per 100km or km per liter. Because a US gallon (3.785 liters) is meaningfully smaller than a UK/Imperial gallon (4.546 liters), the same car can show two different MPG numbers depending on which gallon is used — and because MPG-style units run in the opposite direction from L/100km, mixing them up while comparing cars can make an inefficient vehicle look efficient, or vice versa.

Real-World Applications

• Comparing a US-market car's MPG rating against a European model's L/100km spec
• Converting a UK vehicle listing's Imperial MPG into US MPG before buying or importing
• Estimating typical running costs for a rental car in a country using different fuel efficiency units
• Checking whether a hybrid or EV efficiency claim genuinely beats a comparable gas car once units are aligned
• Pairing with NeftCal's Fuel Cost Calculator and Trip Cost Calculator to turn a converted efficiency figure into an actual trip budget

If your input was MPG (US) or MPG (UK): a bigger number after conversion means the car goes further on the same amount of fuel — so when comparing two MPG figures, the larger one is the more efficient vehicle.

If your input was L/100km: a smaller number after conversion means the car needs less fuel to cover the same distance — so when comparing two L/100km figures, the smaller one is the more efficient vehicle. This is the opposite direction from MPG, which is the single most common point of confusion when reading international fuel economy specs side by side.

Km/L behaves like MPG (higher is better), since both describe distance covered per unit of fuel, just in different base units (miles vs kilometers, gallons vs liters).