⛽ Fuel Economy Converter (MPG, L/100km)
Convert fuel economy between US MPG, UK MPG, litres per 100 km and kilometres per litre — with the US-vs-UK gallon difference handled correctly.
US MPG
30
mpg
UK (imperial) MPG
36.03
mpg
Litres / 100 km
7.84
L
Kilometres / litre
12.75
km/L
The US and UK gallons differ (3.785 L vs 4.546 L), so US MPG and UK MPG are NOT the same — 30 US mpg is about 36 UK mpg. L/100 km is an inverse measure: lower is better. 🔒 In your browser.
How the fuel economy converter (mpg, l/100km) works
Every figure is converted through a common basis using the exact unit definitions: the US gallon is 3.785 L, the imperial (UK) gallon is 4.546 L, and a mile is 1.609 km. Miles-per-gallon is a distance-per-fuel measure (higher is better), while litres-per-100-km is fuel-per-distance (lower is better) — the tool inverts correctly between them.
The big trap is that a US MPG and a UK MPG are not the same, because the gallons differ by about 20%. A car rated 30 US mpg is about 36 UK mpg — same car, different number. Always check which gallon a figure uses.
Frequently asked questions
How do I convert MPG to L/100km?
For US MPG, litres per 100 km = 235.21 ÷ MPG. So 30 US mpg is 235.21 ÷ 30 ≈ 7.84 L/100km. For UK MPG use 282.48 ÷ MPG instead, because the imperial gallon is larger.
Is US MPG the same as UK MPG?
No. The US gallon (3.785 L) is smaller than the imperial gallon (4.546 L), so the same real economy gives a higher number in UK MPG. 30 US mpg equals about 36 UK mpg.
Is a lower L/100km better or worse?
Lower is better — litres per 100 km measures how much fuel you use to cover a fixed distance, so using fewer litres is more efficient. It’s the opposite sense to MPG, where higher is better.
How do I convert L/100km to MPG?
US MPG = 235.21 ÷ (L/100km); UK MPG = 282.48 ÷ (L/100km). For 5 L/100km that’s about 47 US mpg or 56 UK mpg. The tool does all four units at once.
What is km per litre?
Kilometres travelled per litre of fuel — common in many countries. It equals 100 ÷ (L/100km); higher is better. For example, 7.84 L/100km is about 12.75 km/L.