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Calculator Answers

Fuel Economy Converter

Blake Boege
Written by Blake Boege · Founder, Calculator Answers

A fuel economy converter is a transportation measurement utility that translates vehicle fuel efficiency values between different unit systems. The converter supports conversions between distance-per-volume units (such as miles per gallon in US and UK standards) and volume-per-distance units (such as liters per one hundred kilometers). It applies reciprocal mathematical formulas to resolve the inverse relationship between these measurement styles. Drivers, automotive researchers, and international travelers use this tool to compare fuel efficiency ratings across different regions.

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.

See also: Power Converter, Angle Converter, and Frequency Converter.

Quick Answer

Convert fuel consumption values between metric and imperial systems. Enter the economy value and select units to calculate conversions between miles per gallon and liters per 100km.

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.

Fuel economy

Miles per gallon → Liters per 100 km

7.8405 L/100 km

30 mpg US = 7.8405 L/100 km

Miles per gallon, US (mpg US)30 mpg US
Miles per gallon, Imperial (mpg UK)36.0285 mpg UK
Kilometers per liter (km/L)12.7543 km/L
Miles per liter (mi/L)7.9252 mi/L
Liters per 100 km (L/100 km)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.

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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.