How to use the fuel consumption converter
Choose the unit you have in From and the unit you want in To, type the value and press Convert. The value must be greater than zero, for the reason explained in the questions at the end of this page.
Two opposite kinds of unit
Fuel economy is expressed in two ways that run in opposite directions:
- Fuel per distance, such as liters per 100 kilometers (L/100 km) or gallons per 100 miles. A lower number means less fuel used.
- Distance per fuel, such as miles per gallon (mpg), kilometers per liter (km/L) or miles per liter. A higher number means less fuel used.
Between the two kinds the conversion is a reciprocal, not a multiplication, so doubling a value in L/100 km halves it in mpg. Within one kind, only a scale factor changes. The converter turns every value into kilometers per liter and then into the target unit, using exact definitions: one mile is 1.609344 km, one US gallon is 3.785411784 L and one imperial gallon is 4.54609 L.
Fuel economy formulas
| From | To | Formula |
|---|---|---|
| L/100 km | mpg (US) | mpg (US) = 235.2146 ÷ L/100 km |
| L/100 km | mpg (UK) | mpg (UK) = 282.4809 ÷ L/100 km |
| L/100 km | km/L | km/L = 100 ÷ L/100 km |
| mpg (US) | mpg (UK) | mpg (UK) = mpg (US) × 1.20095 |
| mpg (UK) | mpg (US) | mpg (US) = mpg (UK) × 0.832674 |
| mpg (US) | km/L | km/L = mpg (US) × 0.425144 |
| mpg (US) | gal (US)/100 mi | gal/100 mi = 100 ÷ mpg |
Worked examples
- 6.5 L/100 km to mpg: 235.2146 ÷ 6.5 ≈ 36.19 mpg (US), and 282.4809 ÷ 6.5 ≈ 43.46 mpg (UK).
- 30 mpg (US) to L/100 km: 235.2146 ÷ 30 ≈ 7.84 L/100 km.
- 50 mpg (UK) to L/100 km: 282.4809 ÷ 50 ≈ 5.65 L/100 km, which is about 41.63 mpg (US).
- 15 km/L to L/100 km: 100 ÷ 15 ≈ 6.67 L/100 km.
L/100 km to miles per gallon
| L/100 km | mpg (US) | mpg (UK) | km/L |
|---|---|---|---|
| 3 | 78.4 | 94.16 | 33.33 |
| 4 | 58.8 | 70.62 | 25 |
| 5 | 47.04 | 56.5 | 20 |
| 6 | 39.2 | 47.08 | 16.67 |
| 7 | 33.6 | 40.35 | 14.29 |
| 8 | 29.4 | 35.31 | 12.5 |
| 9 | 26.13 | 31.39 | 11.11 |
| 10 | 23.52 | 28.25 | 10 |
| 12 | 19.6 | 23.54 | 8.33 |
| 15 | 15.68 | 18.83 | 6.67 |
| 20 | 11.76 | 14.12 | 5 |
US miles per gallon to L/100 km
| mpg (US) | L/100 km | mpg (UK) | km/L |
|---|---|---|---|
| 10 | 23.52 | 12.01 | 4.25 |
| 15 | 15.68 | 18.01 | 6.38 |
| 20 | 11.76 | 24.02 | 8.5 |
| 25 | 9.41 | 30.02 | 10.63 |
| 30 | 7.84 | 36.03 | 12.75 |
| 35 | 6.72 | 42.03 | 14.88 |
| 40 | 5.88 | 48.04 | 17.01 |
| 50 | 4.7 | 60.05 | 21.26 |
| 60 | 3.92 | 72.06 | 25.51 |
Imperial miles per gallon to L/100 km
| mpg (UK) | L/100 km | mpg (US) |
|---|---|---|
| 20 | 14.12 | 16.65 |
| 30 | 9.42 | 24.98 |
| 40 | 7.06 | 33.31 |
| 50 | 5.65 | 41.63 |
| 60 | 4.71 | 49.96 |
| 70 | 4.04 | 58.29 |
US and imperial mpg are different
An imperial gallon is about 20% larger than a US gallon, so the same car covers more miles on it and shows a higher mpg figure in the United Kingdom than in the United States. One US mpg is about 1.201 imperial mpg. The United Kingdom sells fuel by the liter but still commonly quotes economy in imperial mpg, so a figure from a British source should be converted with the mpg (UK) unit. Mixing the two up is an easy mistake when comparing cars across countries.
Why mpg can mislead: 10 to 20 versus 30 to 40
Because mpg is distance per fuel, equal steps in mpg do not save equal amounts of fuel. Converting to gallons per 100 miles shows the fuel actually used:
| mpg (US) | gal (US)/100 mi | L/100 km |
|---|---|---|
| 10 | 10 | 23.52 |
| 20 | 5 | 11.76 |
| 30 | 3.33 | 7.84 |
| 40 | 2.5 | 5.88 |
Going from 10 to 20 mpg cuts fuel from 10 to 5 gallons per 100 miles, a saving of 5 gallons. Going from 30 to 40 mpg cuts it from about 3.33 to 2.5 gallons, a saving of about 0.83 gallons. Over 10,000 miles that is 500 gallons against about 83 gallons. For the same distance driven, raising a low mpg figure saves more fuel than raising a high one by the same amount. Units of fuel per distance, such as L/100 km, avoid this trap: a drop of 1 L/100 km saves the same fuel whatever the starting point.
Common pitfalls
- Averaging mpg values. If you drive 100 miles at 20 mpg and 100 miles at 40 mpg, you use 5 + 2.5 = 7.5 gallons for 200 miles, which is about 26.67 mpg, not 30. Averages of L/100 km over equal distances do work, because they measure fuel directly.
- Multiplying instead of inverting. No single factor turns L/100 km into mpg. A higher L/100 km always means a lower mpg.
- Comparing different test methods. Converting units does not make ratings comparable if they come from different official test procedures, which vary between regions. Compare figures measured the same way.
Frequently asked questions
How do I convert L/100 km to mpg?
Divide about 235.2146 by the L/100 km value for US mpg, or about 282.4809 for imperial mpg. For example, 8 L/100 km is about 29.40 mpg (US).
Is a lower or higher number better?
For L/100 km and gallons per 100 miles, lower is better. For mpg, km/L and miles per liter, higher is better.
How do I convert km/L to L/100 km?
Divide 100 by the km/L value. The same formula works in reverse, so 10 L/100 km is 10 km/L and 5 L/100 km is 20 km/L.
Why can't I enter zero?
Every conversion between the two kinds of unit divides by the value, and zero has no reciprocal. Negative values are also rejected because fuel use cannot be negative.
Supported units
- Liters per 100 kilometers (L/100 km)
- Kilometers per liter (km/L)
- Miles per gallon (US) (mpg (US))
- Miles per gallon (imperial) (mpg (UK))
- Miles per liter (mi/L)
- US gallons per 100 miles (gal (US)/100 mi)
- Imperial gallons per 100 miles (gal (UK)/100 mi)