What is Fuel Conversion?
Convert fuel consumption units between km/L, L/100km, and miles per gallon (US/UK). Higher km/L or mpg means better efficiency; lower L/100km means less fuel used.
Supported units: Kilometer/Liter (km/L), Liter/100km (L/100km), Miles/Gallon (US) (mpg(US)), Miles/Gallon (UK) (mpg(UK)).
Why fuel efficiency has three unit systems that point in opposite directions
Fuel economy is the rare quantity where the unit itself flips the meaning. km/L and mpg (US or UK) measure distance per fuel — higher is better. L/100 km measures fuel per distance — lower is better. Both approaches are valid, but they lead to different intuitions. L/100 km (the European and most Asian standard) is also linear with fuel cost: if a car uses 8 L/100 km, a 400 km trip uses exactly 32 L. Converting between the two systems isn't a simple multiplier — it's a reciprocal: L/100 km = 100 ÷ (km/L). Then there's the gallon problem: US mpg uses the 3.785 L gallon, UK mpg uses the 4.546 L imperial gallon, so a UK car rated "40 mpg" gets only about 33 US mpg — same car, 20 % smaller number. Any time someone quotes an mpg figure, always ask which gallon.
Where you need fuel conversions
Buying or comparing cars
Manufacturers quote efficiency in whichever unit sells best locally. A Japanese car might list 20 km/L; a US spec for the same model shows 47 mpg; a European spec shows 5 L/100 km. Converting lets you know if a spec sheet is genuinely better or just re-expressed.
Road trip fuel budgeting
If you know your car does 6 L/100 km and you're planning a 1,200 km drive, you need 72 L — roughly $100 at European prices. This linear relationship makes L/100 km the easiest for budgeting, which is why Europe adopted it.
Fleet management
Logistics companies track usage in L/100 km because fuel is a major cost line and linear units make spreadsheet math straightforward. A 5 % efficiency improvement translates directly to 5 % lower fuel spend.
EV comparisons
Electric vehicles are rated in kWh/100 km (Europe) or MPGe (US — "miles per gallon equivalent", using 33.7 kWh per gallon of gasoline). An EV at 15 kWh/100 km converts to about 157 MPGe. These numbers let you compare efficiency across very different fuels.
Tax and environmental incentives
Many countries set vehicle taxes by CO₂ emissions, calculated from L/100 km × fuel energy density. A clean conversion is the difference between a tax rebate and a surcharge.
Common Conversions
- 1 Kilometer/Liter (km/L) = 100 Liter/100km (L/100km)
- 1 Kilometer/Liter (km/L) = 2.35215 Miles/Gallon (US) (mpg(US))
- 1 Liter/100km (L/100km) = 100 Kilometer/Liter (km/L)
- 1 Liter/100km (L/100km) = 235.215 Miles/Gallon (US) (mpg(US))
- 1 Miles/Gallon (US) (mpg(US)) = 0.425143 Kilometer/Liter (km/L)
- 1 Miles/Gallon (US) (mpg(US)) = 235.215 Liter/100km (L/100km)
FAQ
Q: How to convert km/L to L/100km?
A: L/100km = 100 ÷ (km/L). Example: 15 km/L = 100 ÷ 15 ≈ 6.67 L/100km.
Q: How to convert km/L to mpg (US)?
A: Multiply by 2.35215. Example: 10 km/L × 2.35215 ≈ 23.5 mpg.
Q: What is the difference between US and UK mpg?
A: UK gallon (4.546 L) is larger than US gallon (3.785 L), so UK mpg is always higher. 1 km/L ≈ 2.352 mpg(US) ≈ 2.825 mpg(UK).
Q: Why is L/100 km considered a better measure than mpg?
A: Because it's linear with fuel consumption: twice the distance at the same L/100 km means exactly twice the fuel. MPG is inversely proportional — a car going from 15 to 20 mpg saves far more fuel than one going from 40 to 45 mpg, which isn't intuitive at a glance.
Q: How do I compare an EV to a petrol car?
A: Use MPGe (US) or kWh/100 km (Europe). MPGe uses the convention that 33.7 kWh ≈ 1 US gallon of gasoline by energy content. An EV at 3 mi/kWh = 100 MPGe; one at 4 mi/kWh = 135 MPGe. Comparing to a 30-mpg petrol car makes the efficiency gap very visible.