Fuel Efficiency & Trip Cost Calculator
Convert between MPG and L/100km, and calculate the fuel cost of a journey.
Formula
L/100km = 235.214583 / MPG(US)
Tips
- MPG and L/100km are inverse measures: higher MPG is better, lower L/100km is better.
- A US gallon is about 3.785 L; an Imperial gallon is about 4.546 L, so UK MPG figures look ~20% better than US figures for the same car.
- Improving from 15 to 20 MPG saves more fuel per mile than improving from 40 to 50 MPG — the inverse relationship is counterintuitive.
Frequently asked questions
Where does the constant 235.214583 come from?
It is 100 × 3.785411784 (litres per US gallon) ÷ 1.609344 (km per mile), the factor that converts miles-per-gallon into litres-per-100-kilometres.