MPG to L/100km Converter
Convert UK MPG (miles per gallon, Imperial) to L/100km — the UK fuel economy converter.
Last updated: 2026-07-25
Miles per gallon (Imperial gallon = 4.546 L)
Litres per 100 kilometres
UK MPG
40
miles per gallon (Imperial)
L/100km
7.1
litres per 100 km
Formula: L/100km = 282.48 ÷ MPG (UK Imperial gallon = 4.546 L)
Lower L/100km = better fuel economy. A typical UK family car does about 40-50 mpg (5.6–7.1 L/100km). Note: US MPG uses a different gallon (3.785 L) — US formula is 235.2 ÷ MPG.
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UK fuel economy is measured in miles per gallon (mpg) using Imperial gallons (4.546 L). Most of Europe uses litres per 100 kilometres (L/100km). The conversion is not a simple multiply — it works the other way round: L/100km = 282.48 ÷ MPG. This converts both ways, so you can compare UK and European car specs without the arithmetic.
Frequently asked questions
How do I convert UK MPG to L/100km?
Divide 282.48 by the MPG figure. For example, 40 mpg ÷ 282.48 ≈ 7.1 L/100km. The constant 282.48 comes from converting Imperial gallons (4.546 L) and miles (1.609 km): (100 × 4.54609) ÷ 1.609344 = 282.48. Lower L/100km means better fuel economy.
Is UK MPG the same as US MPG?
No. UK MPG uses the Imperial gallon (4.546 litres); US MPG uses the US gallon (3.785 litres) — about 20% smaller. So a car rated at 40 mpg (UK) would only show about 33 mpg in a US test. The US formula is L/100km = 235.2 ÷ MPG (US). Always check which gallon a review or spec sheet uses, especially when comparing UK and US car reviews.
What is a good MPG in the UK?
A typical UK family petrol car gets about 40-50 mpg (5.6–7.1 L/100km). Diesel cars often achieve 55-65 mpg (4.3–5.1 L/100km). Hybrids can reach 60-80 mpg (3.5–4.7 L/100km). Anything above 50 mpg is considered excellent; below 30 mpg is relatively thirsty for a modern car.
Why does the UK still use MPG when Europe uses L/100km?
The UK kept miles on road signs and MPG for fuel economy after metrication, unlike the rest of Europe. New UK car ads and specs show both MPG and L/100km by law since 2020, but MPG remains the number most British drivers understand.