Fuel Economy Converter
mpg, km/L and L/100km.
Convert
Result
235.2145836 L/100km
1 miles per gallon (us) in litres per 100 km
1 mpg = 235.2145836 L/100km
Fuel Economy Conversion Math Formula
Fuel economy is the one family where the usual method breaks. Miles per gallon and kilometres per litre measure distance per fuel, so more is better. Litres per 100 km measures fuel per distance, so less is better. Converting between the two kinds means taking a reciprocal, and that makes the relationship a curve instead of a straight line.
If a car does 12.5 km/L, then 1 km takes 1/12.5 = 0.08 L and 100 km takes 8 L. So 12.5 km/L is 8 L/100 km. As the first number goes up the second goes down. The converter passes through km/L and applies the reciprocal wherever it is needed.
The formula
L/100 km = 100 ÷ (km/L)L/100 km = 235.215 ÷ mpg (US)L/100 km = 282.481 ÷ mpg (UK)km/L = mpg (US) × 0.425144 = mpg (UK) × 0.354006
Worked example 1: 30 mpg (US), in L/100 km
30 mpg × 0.425143707 = 12.7543 km/L100 ÷ 12.7543 km/LAnswer: 7.84049 L/100km
The shortcut 235.215 ÷ 30 gives the same 7.84. Remember that a bigger mpg means a smaller L/100 km.
Worked example 2: 6.5 L/100 km, in mpg (US)
100 ÷ 6.5 = 15.3846 km/L15.3846 km/L ÷ 0.425143707Answer: 36.1869 mpg
The same car reads 43.46 mpg on the UK scale, because an imperial gallon is about 20% larger.
Worked example 3: A trip of two legs at 20 mpg and 40 mpg, as L/100 km
Leg 1: 100 miles at 20 mpg uses 5 gallonsLeg 2: 100 miles at 40 mpg uses 2.5 gallons200 miles on 7.5 gallons = 26.6667 mpg, not (20 + 40) ÷ 2 = 30Answer: 8.82055 L/100km
Fuel use adds up, so average the fuel per distance, not the distance per fuel. In L/100 km it comes out directly: (11.76 + 5.88) ÷ 2 = 8.82.
Common mistakes to avoid
- Using a straight multiplier on L/100 km. You cannot go from mpg to L/100 km by multiplying. 10 mpg is 23.5 L/100 km, 20 mpg is 11.8 and 40 mpg is 5.88. Doubling the mpg halves the consumption. It does not double it.
- Mixing US and UK mpg. A UK gallon is 4.546 L against 3.785 L, so 40 mpg (UK) is about 33.3 mpg (US). The two figures are never interchangeable.
- Assuming every mpg gain is worth the same. Going from 10 to 20 mpg saves 500 gallons over 10,000 miles (1,000 down to 500). Going from 30 to 50 mpg saves only about 133 gallons (333 down to 200). L/100 km shows this honestly. mpg hides it.
About fuel economy units
Fuel economy tells you how far a vehicle goes on a given amount of fuel, or how much fuel it burns over a distance. The US uses miles per US gallon. The UK quotes miles per imperial gallon. Much of Europe, Canada, Australia and China quote litres per 100 km, and some countries, including Japan and India, use kilometres per litre.
Litres per 100 km has the clearest meaning, because it measures fuel burned, which is what you pay for. It also adds up: you can sum the fuel for two trips. This tool flips between all four conventions using exact mile and gallon definitions.
- Kilometre per litre (km/L)Distance per litre. Higher is better.
- Litres per 100 km (L/100km)Litres of fuel per 100 kilometres. Lower is better. It equals 100 ÷ (km/L).
- Miles per gallon (US) (mpg)1 mpg = 0.425143707 km/LUS miles per US gallon. 1 mpg is 0.425144 km/L.
- Miles per gallon (UK) (mpg UK)1 mpg UK = 0.354006189 km/LMiles per imperial gallon. 1 mpg (UK) is 0.354006 km/L, which is 1.20095 mpg (US).
Fuel Economy conversion table
| Value | km/L | L/100km | mpg | mpg UK |
|---|---|---|---|---|
| 5 L/100km | 20 | 5 | 47.0429 | 56.4962 |
| 6 L/100km | 16.6667 | 6 | 39.2024 | 47.0802 |
| 8 L/100km | 12.5 | 8 | 29.4018 | 35.3101 |
| 10 L/100km | 10 | 10 | 23.5215 | 28.2481 |
| 12 L/100km | 8.33333 | 12 | 19.6012 | 23.5401 |
Fuel Economy converter FAQ
How do I convert mpg to L/100 km?
Divide 235.215 by the mpg figure. 25 mpg gives 235.215 ÷ 25 = 9.41 L/100 km. For a UK mpg figure, divide 282.481 instead.
How do I convert L/100 km to mpg?
Divide 235.215 by the L/100 km figure. 8 L/100 km gives 235.215 ÷ 8 = 29.4 mpg (US). In UK gallons it is 282.481 ÷ 8 = 35.3 mpg.
Why is a lower L/100 km better when a higher mpg is better?
They are reciprocals. mpg counts distance per fuel, so a bigger number means more distance from each unit of fuel. L/100 km counts fuel per distance, so a bigger number means more fuel burned. Same car, opposite direction.
How do I calculate my own fuel economy?
Fill the tank, note the odometer, drive, fill again and note the litres added. Distance divided by litres gives km/L. A trip of 450 km that took 32 L is 450 ÷ 32 = 14.06 km/L, which is 7.11 L/100 km or 33.1 mpg (US).
What is the difference between US and UK mpg?
The imperial gallon is about 20% bigger than the US gallon (4.546 L against 3.785 L), so the same car has a higher mpg figure on the UK scale. 30 mpg (US) is about 36 mpg (UK).
How many km/L is one mpg?
0.4251 km/L for a US gallon. Going the other way, 1 km/L is 2.3521 mpg (US) and 2.8248 mpg (UK).