US miles per gallon to liters per 100 km converter

A US miles-per-gallon rating describes distance traveled for a fixed fuel amount. Converting it to consumption per distance reverses the scale: a larger mpg value becomes a smaller liters-per-100-kilometers value. UK imperial mpg needs a different gallon definition.

Divide 235.214583 by the value: 30 US mpg is 235.214583 ÷ 30 = 7.84 L/100 km, and 6 L/100 km is 235.214583 ÷ 6 = 39.2 mpg. The same formula works in both directions because each unit is the reciprocal of the other, scaled.

Accuracy depends on your inputs and the method's assumptions. Decimal arithmetic uses 50 significant digits, but estimates, numerical methods and source data can be less precise; the displayed rounding does not remove those limits. It is checked against 3 worked examples whose answers come from independent sources; for example, “30 mpg (US) to L/100 km” is checked against Exact-fraction computation from the legal unit definitions (scripts/gen-pairs.py, Python fractions).

NIST SP 811 (2008), Guide for the Use of the International System of Units, Appendix B; NIST Handbook 44, Appendix C: General tables of units of measurement; BIPM, The International System of Units (SI Brochure), 9th edition.