How do I convert MPG to L/100km?

Divide 235.21 by US MPG. For UK MPG, divide 282.48 by the figure.

How do I convert km/L to MPG?

Multiply km/L by 2.352 for US MPG, or by 2.825 for UK MPG.

6 L/100km is about 39 US MPG, which is efficient for a petrol car, though typical for a small hybrid or diesel.

Why is UK MPG different from US MPG?

An imperial gallon is about 20% larger than a US gallon, so the same car shows about 20% higher MPG in UK units.

Which is better, a higher or lower L/100km?

Lower. L/100km is fuel used per distance, so a smaller number means less fuel.

Fuel Economy Converter: MPG to L/100km / CarO

Written by Muneeb Rana · Last updated 21 October 2026

Quick answer: A fuel economy converter switches between MPG, L/100km and km/L. The key formulas: L/100km = 235.21 ÷ US MPG, or 282.48 ÷ UK MPG; km/L = US MPG × 0.4251. So 30 US MPG equals about 7.8 L/100km, 12.8 km/L and 36 UK MPG. Lower L/100km is better; higher MPG is better.

TL;DR

Type a value in any unit and the others update.
UK MPG uses the larger imperial gallon.
L/100km is 'lower is better'.

This fuel economy converter translates any figure between US MPG, UK (imperial) MPG, litres per 100 km and kilometres per litre. It's useful when comparing cars across countries, reading reviews from other markets, or setting up a fuel log in different units.

How to use the fuel economy converter

Type a number in any box: US MPG, UK MPG, L/100km or km/L.
The other three update instantly.
Use the table below for common values.
Copy the result or switch to the MPG calculator to work out your own figure.

How the fuel economy converter works

us_gallon = 3.78541 L ; uk_gallon = 4.54609 L ; mile = 1.609344 km
km_per_l      = us_mpg * 1.609344 / 3.78541   (= us_mpg * 0.425144)
l_per_100km   = 235.215 / us_mpg              (= 282.481 / uk_mpg)
uk_mpg        = us_mpg * 1.20095

US MPG	UK MPG	L/100km	km/L
20	24.0	11.8	8.5
25	30.0	9.4	10.6
30	36.0	7.8	12.8
35	42.0	6.7	14.9
40	48.0	5.9	17.0
50	60.0	4.7	21.3

Worked example

A European review lists a car at 5.5 L/100km. 235.21 ÷ 5.5 = 42.8 US MPG, or 282.48 ÷ 5.5 = 51.4 UK MPG, or 100 ÷ 5.5 = 18.2 km/L.

Why L/100km and MPG feel backwards

MPG measures distance per fuel (higher is better). L/100km measures fuel per distance (lower is better). Because of that, savings don't scale evenly: going from 10 to 20 MPG saves far more fuel over 100 miles than going from 40 to 50 MPG. That's why some countries prefer fuel-per-distance figures. FuelEconomy.gov also shows gallons per 100 miles for this reason.

Use the right figure for your budget

For costs, plug the converted figure into the fuel cost calculator. For EVs, efficiency is usually kWh per 100 miles; see the EV charging cost calculator.

Keep your own numbers

Logging fill-ups in a fuel log lets you work out your own economy in any unit, see how to calculate MPG and how to improve fuel economy.

Download CarO free on the App Store or Google Play. Free with ads; optional in-app purchases.

Sources

FuelEconomy.gov: Find and Compare Cars: www.fueleconomy.gov (accessed 21 October 2026)
FuelEconomy.gov: Keeping Your Vehicle in Shape: www.fueleconomy.gov (accessed 21 October 2026)

Disclaimer: CarO and this website give general car-care information, not professional advice. Maintenance intervals and specifications vary by vehicle, so always follow your owner's manual and a qualified mechanic. Mileage and cost figures are estimates; check local tax rules before using any log for deductions.

Fuel Economy Converter