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Fuel Economy Converter Guide

Convert fuel economy between km/L, L/100 km and US or UK MPG.

Fuel economy says how far a vehicle travels per amount of fuel. Fuel Economy Converter shows four ways of writing the same consumption: km/L, L/100 km, US MPG, and UK MPG. MPG means miles per gallon; US and UK gallons differ.

Try an easy reciprocal

Set Value to 10 and Unit to L/100 km. The table should show 10 for L/100 km and 10 for km/L, because 100 ÷ 10 = 10. The US and UK MPG rows should show about 23.521 and 28.248, respectively. Change Value to 0: the numbers become dashes and the page asks for a value greater than zero. Correct the value to resume.

There is no copy button; read the table or note the values you need. These are unit conversions, not a prediction of your actual vehicle’s fuel use. Outputs are rounded to at most three decimal places for display, so do not expect a copied rounded number to reproduce the original with unlimited precision.

Where your input goes

Processing runs in your browser. The tool does not upload your input to ilham.dev.

For more background, read Calculators and Unit Conversion.

Questions you might have

Why are there two MPG values?
Because the US and UK gallons are not the same size. A UK gallon is about 20% larger, so the same car always shows a higher UK MPG figure. The converter keeps both so a review or a spec sheet written in either country can be read without guessing.
Which direction is better?
Higher km/L and higher MPG are better; lower L/100 km is better. That inversion is the usual reason a plain percentage change is confusing — a 10% drop in L/100 km is an improvement, not a loss.
How is L/100 km converted?
It is the reciprocal relationship: L/100 km equals 100 divided by km/L, and km/L equals 100 divided by L/100 km. That is why the two curves are not linear and small L/100 km figures turn into very large km/L figures.
What are the exact MPG factors?
This implementation multiplies km/L by 2.352145833 for US MPG and 2.824809 for UK MPG. Those factors are rounded constants in the code, not a claim of exact precision beyond the displayed digits.
Is the result rounded?
Each value is rounded to at most three decimal places for display, with trailing zeros omitted. The calculation happens before this display rounding.