How do I convert UK mpg to L/100km?

Divide 282.481 by the UK mpg figure. For example, 50 UK mpg = 282.481 / 50 = 5.6 L/100km. Note this uses the UK imperial gallon (4.546 litres), not the smaller US gallon.

Why is L/100km the opposite way around to mpg?

MPG measures distance per unit of fuel (higher is better), while L/100km measures fuel per unit of distance (lower is better). This inverse relationship means you cannot simply multiply by a factor to convert — you must divide.

What is the difference between UK mpg and US mpg?

UK mpg uses the imperial gallon (4.546 L) while US mpg uses the smaller US gallon (3.785 L). UK mpg figures are about 20% higher than US mpg for the same real-world consumption. Always check which gallon is being used.

What is considered good fuel economy in L/100km?

Below 5 L/100km is excellent, 5-7 L/100km is good, 7-10 L/100km is average, and above 10 L/100km is poor. Hybrid cars can achieve 3-4 L/100km in mixed driving.

Why can I not just multiply to convert MPG to L/100km?

Because MPG and L/100km are inversely related. MPG measures distance per fuel unit (higher is better), while L/100km measures fuel per distance (lower is better). You must divide the conversion constant (282.481 for UK MPG) by the value, not multiply.

CarCalcs

mpg to L/100km Converter

Convert fuel economy between UK mpg and litres per 100km.

Convert From

Choose the unit you want to convert from

Fuel Economy (UK mpg)

Fuel economy value to convert

How We Calculate This

This converter handles the inverse relationship between mpg and L/100km correctly for both UK and US gallons.

The Formulas

UK mpg to L/100km: L/100km = 282.481 / UK mpg
L/100km to UK mpg: UK mpg = 282.481 / L/100km
UK mpg to US mpg: US mpg = UK mpg / 1.20095

Quick Reference

30 UK mpg = 9.4 L/100km
40 UK mpg = 7.1 L/100km
50 UK mpg = 5.6 L/100km
60 UK mpg = 4.7 L/100km

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates. Actual figures may vary based on driving conditions, vehicle specifications, and other factors.