How do I convert mpg to L/100 km?

Divide 235.215 by the mpg (US) value. Example: 30 mpg (US) → 235.215 ÷ 30 = 7.84 L/100 km. For UK mpg divide 282.481 instead.

How do I convert L/100 km to mpg?

Divide 235.215 by the L/100 km value to get US mpg (or 282.481 for UK mpg). Example: 6 L/100 km = 39.2 mpg (US) = 47.1 mpg (UK).

A UK (imperial) gallon is 4.546 liters, about 20% larger than the US gallon (3.785 liters), so the same car shows a higher mpg figure in the UK.

mpg measures distance per fuel (higher is better), while L/100 km measures fuel per distance (lower is better), so one is the inverse of the other.

The constants come from exact definitions: 1 mile = 1.609344 km, 1 US gallon = 3.785411784 L and 1 UK gallon = 4.54609 L.

mpg (US)	L/100 km	mpg (UK)	km/L
10	23.52	12.01	4.25
12	19.6	14.41	5.1
15	15.68	18.01	6.38
18	13.07	21.62	7.65
20	11.76	24.02	8.5
22	10.69	26.42	9.35
25	9.41	30.02	10.63
28	8.4	33.63	11.9
30	7.84	36.03	12.75
32	7.35	38.43	13.6
35	6.72	42.03	14.88
38	6.19	45.64	16.16
40	5.88	48.04	17.01
45	5.23	54.04	19.13
50	4.7	60.05	21.26
55	4.28	66.05	23.38
60	3.92	72.06	25.51

How do I convert mpg to L/100 km?: Divide 235.215 by the mpg (US) value. Example: 30 mpg (US) → 235.215 ÷ 30 = 7.84 L/100 km. For UK mpg divide 282.481 instead.
How do I convert L/100 km to mpg?: Divide 235.215 by the L/100 km value to get US mpg (or 282.481 for UK mpg). Example: 6 L/100 km = 39.2 mpg (US) = 47.1 mpg (UK).
Why are UK and US mpg different?: A UK (imperial) gallon is 4.546 liters, about 20% larger than the US gallon (3.785 liters), so the same car shows a higher mpg figure in the UK.
Why does a bigger mpg mean a smaller L/100 km?: mpg measures distance per fuel (higher is better), while L/100 km measures fuel per distance (lower is better), so one is the inverse of the other.