Miles per US gallon (US mpg): fuel economy unit guide

What is being measured?

Fuel consumption is fuel volume per distance, while economy is distance per fuel volume. The relationship between them is reciprocal and the gallon convention matters.

Fuel consumption and economy are reciprocal. US and imperial gallons differ; inputs must be positive.

Meaning of US mpg

Miles per US gallon uses the symbol US mpg in this library and measures fuel economy. Under the stated reference convention, 1 US mpg = approximately 235.214583333 L/100 km. This equivalence changes how a known value is written. It does not increase measurement accuracy or establish whether a measurement is appropriate to a real application.

Conversion method

This convention uses a reciprocal transformation. Doubling a consumption quantity halves its reciprocal economy quantity; a constant multiplier is not appropriate.

Worked example

For a known value of 10 US mpg, the reference conversion gives 23.5214583333 L/100 km. Converting that result back gives approximately 10 US mpg. This reverse check helps catch a reversed factor, but matching round-trip arithmetic alone does not independently verify a source definition.

Common reference values

Compare one US mpg with other units

Precision and common mistakes

• Keep the source and target quantity consistent. A matching symbol is not enough to establish a compatible definition.
• Record the original measurement precision. Showing twelve significant digits in a table does not make a rounded input more precise.
• Check symbol capitalization, prefixes and any regional convention in the source. Use the displayed unit definition rather than a similarly named unit.
• Factors involving repeating fractions or π use finite numerical precision. Round the final answer to the precision justified by your input.

Use a working converter

• Fuel economy converter
• Miles per US gallon to uk mpg converter
• Miles per US gallon to Litres per 100 km converter
• Miles per US gallon to kilometers per liter converter
• Miles per US gallon to miles per liter converter

Source and verification scope

Examples and tables are computed from the versioned unit definitions used by the linked converters. The source access dates appear below. Computandum is independent of the cited organizations; a citation does not mean that a publisher endorses this page or an actual project.

Read the calculation and sourcing methodology →