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Fuel Economy Converter – MPG to L/100 km and km/L

Convert fuel economy between US miles per gallon, UK miles per gallon, litres per 100 kilometres and kilometres per litre. Add how far you drive in a year and the price of fuel to estimate your yearly fuel use and cost.

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How to use the fuel economy converter

  1. Enter your fuel economy and choose its unit — US MPG, UK MPG, L/100 km or km/L.
  2. Optionally add your distance per year in kilometres and the fuel price per litre.

You’ll see the figure in every unit, and, if you added them, how many litres (and US gallons) you use a year and what it costs.

Conversion formulas

L/100 km = 235.215 ÷ US mpg = 282.481 ÷ UK mpg
UK mpg = US mpg × 1.20095
km/L = US mpg × 0.425144 = 100 ÷ (L/100 km)

Worked example

A car rated at 30 US mpg:

  • L/100 km = 235.215 ÷ 30 = 7.84
  • UK mpg = 30 × 1.20095 = 36.03
  • km/L = 12.75

Driving 15,000 km a year uses 15,000 × 7.84 ÷ 100 ≈ 1,176 litres (about 311 US gallons). At 1.80 a litre, that’s about 2,117 a year in your currency.

Why L/100 km makes comparisons easier

Because L/100 km measures fuel used rather than distance travelled, savings are easy to compare. Going from 10 to 5 L/100 km saves 5 litres every 100 km. In MPG the same change looks like 23.5 to 47 mpg, and an improvement from 47 to 70 mpg saves much less fuel than one from 15 to 20 mpg — a common source of confusion when choosing a car.

Which countries use which unit

  • United States: miles per US gallon.
  • United Kingdom: miles per imperial gallon, though fuel is sold in litres.
  • Canada, Europe, Australia and South Africa: litres per 100 km.
  • India, Japan, much of Latin America and parts of Africa: kilometres per litre.

Tips to use less fuel

  • Drive smoothly — gentle acceleration and early braking can save 10% or more.
  • Keep tyres at the right pressure.
  • Remove roof boxes and extra weight when you don’t need them.
  • Keep to the speed limit — fuel use rises quickly above about 90 km/h (55 mph).
  • Service the car regularly.

Official ratings vs real life

Official figures come from standard laboratory tests, which differ between countries — the US uses EPA ratings, while Europe and many other countries use the WLTP cycle. Real-world economy is often 10% to 20% worse, depending on traffic, weather, speed and driving style.

Convert distances with the miles to km converter, or see the full cost of a car with the auto loan calculator.

Frequently asked questions

How do I convert MPG to L/100 km?

For US MPG, divide 235.215 by the MPG: 30 US mpg = 235.215 ÷ 30 = 7.84 L/100 km. For UK MPG, divide 282.481 by the MPG: 40 UK mpg = 7.06 L/100 km.

Why are US and UK MPG different?

A UK (imperial) gallon is 4.546 litres and a US gallon is 3.785 litres — about 20% smaller. The same car shows a higher MPG in the UK: 30 US mpg is about 36 UK mpg.

Is a higher or lower number better?

For MPG and km/L, higher is better — you travel further on each unit of fuel. For L/100 km, lower is better — you use less fuel to travel 100 km.

What is good fuel economy?

It depends on the vehicle. Many modern small petrol cars manage around 5 to 6 L/100 km (40 to 47 US mpg), while large SUVs and pickups often use 10 L/100 km or more (under 24 US mpg).

How do I work out my yearly fuel cost?

Enter your distance per year in kilometres and your fuel price per litre. The converter multiplies the distance by your L/100 km, divides by 100 and multiplies by the price.

How do I measure my real fuel economy?

Fill the tank, reset the trip meter, drive normally, then fill up again. Divide the litres added by the kilometres driven and multiply by 100 for L/100 km.

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