Converters
Fuel Economy Converter
Pick a 'from' unit and a 'to' unit, enter a positive value, and the converter returns all common fuel economy units. The math handles the inverse nature of L/100 km automatically.
Positive numbers only. Fuel economy is undefined at zero. · e.g. 30
Internal base unit is km/L. mpg and mi/L scale linearly; L/100 km is inverse and uses 100 / (km/L) in both directions.
Miles per gallon → Liters per 100 km
7.8405 L/100 km
30 mpg US = 7.8405 L/100 km
mpg US uses the 3.785 L US gallon; mpg Imp uses the 4.546 L British gallon. L/100 km is inverse: lower is more efficient. The others (mpg, km/L, mi/L) are direct: higher is more efficient.
Examples
30 mpg US
≈ 7.84 L/100 km; 36.03 mpg UK; 12.75 km/L
5 L/100 km
≈ 47.04 mpg US; 56.50 mpg UK; 20 km/L
1 km/L
= 100 L/100 km; ≈ 2.352 mpg US
1 mi/L
= 1.609 km/L; ≈ 3.785 mpg US
How it works
The converter uses km/L as a base unit (a "more is better" quantity). It converts the input to km/L, then converts km/L back to the chosen output unit. L/100 km is handled by the inverse identity at both steps.
Inverse identity · km/L = 100 / (L/100 km)
US mpg · L/100 km = 235.214583 / mpg US
Imperial mpg · L/100 km = 282.480936 / mpg UK
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Frequently asked questions
L/100 km expresses fuel consumed per fixed distance: lower is more efficient. mpg, km/L, and mi/L express distance per unit fuel: higher is more efficient. The relationship is inverse, not linear.
A US gallon is 3.785 liters; an Imperial (UK) gallon is 4.546 liters. So 1 mpg US is about 0.833 mpg Imperial. 30 mpg US is roughly 36 mpg Imperial.
Use the identity L/100 km = 235.214583 / mpg US. So 30 mpg US is about 7.84 L/100 km. The calculator does this for you, plus all the other pairs.
No. Fuel economy is only defined for positive values. The calculator flags zero or negative inputs and skips the conversion.
A modern compact car averages 30 to 40 mpg US (6 to 8 L/100 km). A hybrid can reach 50 mpg US (4.7 L/100 km). Large SUVs and trucks may be 15 to 20 mpg US (12 to 16 L/100 km).
No. For electric vehicles, use MPGe (miles per gallon equivalent) from the EPA label or kWh/100 mi for raw energy efficiency. This page handles internal-combustion fuel economy only.
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