⛽ MPG / Fuel Economy Calculator
Turn distance and fuel used into MPG, L/100km, and km/L for a diesel or gasoline truck — and add a fuel price to see exactly what each mile and kilometre costs you.
⛽ Fuel economy
General estimate. Real fuel economy shifts with load, terrain, idling, weather, and driving style — track several tanks for a reliable average and verify with your own records.
Fuel is the biggest line on a truck
For a working diesel, fuel usually dwarfs every other running cost. Even a fraction of a mile per gallon, multiplied across a year of loaded miles, is real money — which is why tracking economy tank by tank pays for itself.
Pair the MPG figure with the fuel-cost calculator to turn economy into a monthly and annual spend, and to see how the fleet total moves when you improve it.
❓ Frequently Asked Questions
How is MPG calculated?
Miles per gallon is simply the distance driven divided by the fuel used: 600 miles on 100 US gallons is 6.0 MPG. In metric, litres per 100 km is fuel ÷ distance × 100. The tool shows MPG, L/100km, and km/L together so you can read the figure in whichever unit you prefer.
How do you convert between MPG and L/100km?
Using 1 US gallon = 3.785 litres and 1 mile = 1.609 km gives the standard constant: L/100km = 235.215 ÷ MPG(US). So 6 MPG is about 39.2 L/100km. Note that US and Imperial gallons differ, so always confirm which gallon your figures use.
How is cost per mile worked out?
Cost per mile = fuel price per gallon ÷ MPG. At $4.00/gal and 6 MPG that is about $0.67 per mile. Divide by 1.609 for cost per kilometre. It is the single most useful number for pricing a load or comparing routes.
Why does my real MPG vary so much?
These are general estimates from the numbers you enter. Load weight, idling, terrain, weather, tire pressure, and driving style all move real fuel economy — track several tanks for a dependable average and verify with your own records rather than a single fill-up.