Miles per US gallon and kilometers per liter
US miles per gallon is the distance in miles driven on one US gallon (3.785 L). EPA window stickers and car reviews in the US quote mpg.
Kilometers per liter is the distance driven on one liter of fuel. Brazil, India, Japan and much of Latin America and Asia rate cars in km/L.
Worked example
Convert 30 mpg: 30 × 0.4251437074 = 12.75431122, so 30 miles per US gallon is 12.75431122 kilometers per liter. Likewise 35 mpg = 14.88002976 km/L.
Estimating in your head
Divide by 2.4 for a quick figure; it is off by about 2%. For 30 mpg that gives 12.5 km/L, against 12.7543 exactly.
Going the other way
To convert kilometers per liter to miles per US gallon, divide by 0.4251437074 (or multiply by 2.35214583333). The swap button between the boxes opens that page.
How this works
km/L = mpg × 0.4251437074
1 mpg = ≈ 0.4251437074 km/L and 1 km/L = 1 km/L, both by definition, so the factor is their ratio: 0.4251437074 (rounded here; the page uses the full value). Results drop binary floating-point noise beyond 15 significant digits and display at the precision you choose (6 significant figures by default). Copy result copies the full value.
Frequently asked
How many kilometers per liter are in a mile per US gallon?
1 mile per US gallon = 0.4251437074 kilometers per liter. The factor is exact by definition but has endless decimals, so it is shown rounded; the page uses the full value.
How do I convert miles per US gallon to kilometers per liter?
Multiply by 0.4251437074. For example, 35 mpg × 0.4251437074 = 14.88002976 km/L.
What is 40 mpg in kilometers per liter?
40 mpg = 17.0057483 km/L. The table next to the converter lists more common values.
Is the result rounded?
Only on screen. The page computes with the exact definitions and removes floating-point noise past 15 significant digits; pick 3 to 12 significant figures, or use Copy result for the full value.
Sources
- NIST Handbook 44 — Appendix C, General tables of units of measurement
- UK Weights and Measures Act 1985, Schedule 1 — Definitions of units
- Wikipedia — Fuel economy in automobiles
Reviewed Oct 17, 2026 · test vectors fixtures/units/fuel/mpg-to-km-l/