How to use this calculator
To convert L/100 km to MPG, choose L/100 km in Input unit, then enter the consumption value. For example, enter 8 to see 29.40 U.S. mpg and 35.31 UK / Imperial mpg. To convert the other way, select the correct MPG gallon definition first, then enter your MPG. Choose km/L if that is the unit on your fuel log. A unit selection changes how the entered number is interpreted; it does not convert that number in place.
A higher MPG or km/L value means more distance per unit of fuel. A lower L/100 km value means less fuel per distance. The calculation uses 1 mile = 1.609344 km, 1 U.S. liquid gallon = 231 cubic inches = 3.785411784 liters, and 1 Imperial gallon = 4.54609 liters. These conversions do not make different vehicle test cycles directly comparable.
The formula
A worked example
30 U.S. mpg equals 7.84 L/100 km, 36.03 UK mpg, and 12.75 km/L. Starting with 8 L/100 km instead gives 29.40 U.S. mpg, 35.31 UK mpg, and 12.50 km/L. Calculations retain full precision internally; displayed results are rounded.
L/100 km to MPG conversion table
Start with metric consumption in the first column. U.S. and Imperial MPG use different gallon sizes; all values are rounded to two decimal places.
| L/100 km | U.S. mpg | UK / Imperial mpg | km/L |
|---|---|---|---|
| 5.00 | 47.04 | 56.50 | 20.00 |
| 6.00 | 39.20 | 47.08 | 16.67 |
| 7.00 | 33.60 | 40.35 | 14.29 |
| 8.00 | 29.40 | 35.31 | 12.50 |
| 10.00 | 23.52 | 28.25 | 10.00 |
| 12.00 | 19.60 | 23.54 | 8.33 |
Common questions
How do I convert L/100 km to MPG?
Select L/100 km as the input unit and enter your consumption. The calculator gives both U.S. and UK MPG. For example, 8 L/100 km is 29.40 U.S. MPG or 35.31 UK MPG.
Why is UK MPG higher than U.S. MPG?
An Imperial gallon contains more fuel than a U.S. liquid gallon. The same fuel efficiency therefore has a UK MPG figure about 20.1% higher. This is a unit difference, not an efficiency improvement.
Why does the conversion use division?
MPG measures distance per fuel volume. L/100 km measures fuel volume per distance, so the relationship is reciprocal. Halving L/100 km doubles MPG.
Can I average two MPG figures to estimate fuel use?
For a measured overall MPG, divide total miles by total gallons. An arithmetic average of MPG figures can misstate the result. For equal-distance trips, averaging L/100 km is appropriate.
Why is zero not accepted?
A finite conversion between these reciprocal measures requires a positive input. Zero fuel consumption would imply infinite distance per fuel unit, which this calculator cannot represent.
Sources & calculation method
The factors are derived from the distance and volume definitions stated above. NIST conversion factors by quantity provides the unit-conversion reference (accessed September 30, 2026). Computation retains full precision before rounding the display.
For readings from a real fill-up, use the MPG Calculator. The fuel-log guide explains how to record distance and fuel consistently. Unit conversion alone does not reconcile differences in vehicle test cycles or driving conditions.
Formula examples and input validation have automated checks. This page has not received an independent automotive professional review. Read our review standards.