MPG and L/100 km: opposite directions
Higher MPG is better economy, while lower L/100 km is better economy.
By the TripFuel team · Updated November 3, 2026
Read the measure correctly
MPG describes distance travelled per unit of fuel. L/100 km describes fuel consumed for a fixed distance. That reverses the direction: a higher MPG value uses less fuel for the same trip, while a higher L/100 km value uses more. Confusing those directions can lead to an unrealistic fuel budget.
Convert with the correct gallon
For US MPG, L/100 km is approximately 235.214583 ÷ MPG. A vehicle at 30 US MPG therefore uses about 7.84 L/100 km. For Imperial MPG, the corresponding constant is approximately 282.480936. The tool uses the exact mile and gallon conversion factors internally, keeping intermediate values unrounded before formatting the final result.
A practical comparison
For 500 km, a car using 6 L/100 km consumes about 30 litres. One using 8 L/100 km consumes about 40 litres. At 1.70 per litre, that is a 17.00 difference in fuel cost for the trip. Compare cars using the same distance, fuel price and return-trip setting. The estimate reflects the economy values you supply; it does not predict the efficiency of a particular vehicle or look up manufacturer test results.
Put the example into practice with the free fuel cost calculator.