MPG Converter

Convert fuel economy between UK MPG, US MPG, litres per 100km and kilometres per litre. Type one figure and see all four.

Reviewed by Dany, RightSums team · Updated

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car-travel · Daily life · UK & US

Type a fuel economy figure, choose its unit and the converter shows it in all four common formats: UK imperial MPG, US MPG, litres per 100 kilometres and kilometres per litre. It converts through L/100km using exact unit sizes: a UK gallon is 4.54609 litres, a US gallon is 3.785411784 litres and a mile is 1.609344 km. That gives UK MPG = 282.481 ÷ L/100km and US MPG = 235.215 ÷ L/100km. Results show to one decimal place, and the formulas are printed under the results. Use it to compare a European car review quoted in L/100km with a UK advert in MPG, or to make sense of an American MPG figure.

Accepted inputs

  • Fuel economy value
  • Unit to convert from (UK MPG, US MPG, L/100km or km/L)

Outputs

  • UK imperial MPG
  • US MPG
  • Litres per 100km (L/100km)
  • Kilometres per litre (km/L)

How to use the MPG Converter

  1. Enter the fuel economy figure you have, such as 45.
  2. Choose its unit: UK MPG, US MPG, L/100km or km/L.
  3. Read the same figure in the other three units, which update as you type.
  4. Check the formula line under the results if you want to do the conversion by hand.

Frequently asked questions

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

Divide 282.481 by the UK MPG figure. 40 UK mpg is 282.481 ÷ 40 = 7.06, shown as 7.1 L/100km. It works the other way too: divide 282.481 by L/100km to get UK MPG, so 6 L/100km is about 47.1 mpg.

Why is US MPG lower than UK MPG for the same car?

Because a US gallon is smaller. It holds 3.785 litres against 4.546 litres for a UK gallon, so a car goes fewer miles on one. 40 UK mpg equals only 33.3 US mpg, even though the car uses exactly the same fuel.

How do I convert US MPG to UK MPG?

Multiply US MPG by about 1.201, the ratio of the two gallon sizes. 30 US mpg is 36.0 UK mpg, or 7.8 L/100km. Select US MPG in the converter and the other three figures appear at once.

Is a lower L/100km figure better?

Yes. L/100km measures fuel used, so lower means more economical, while MPG and km/L measure distance, so higher is better. A car using 5 L/100km does 56.5 UK mpg, 47.0 US mpg and 20 km/L.

What is 50 mpg in km per litre?

50 UK mpg is about 17.7 km/L, and 50 US mpg is about 21.3 km/L. To convert by hand, multiply UK MPG by 0.354 or US MPG by 0.425. The converter handles both gallon sizes, so check which one your figure uses.

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