How this calculator works
Fuel economy links three quantities: distance, fuel volume and the cost of that fuel. If you know the economy and the fuel in the tank, multiplying them gives the range. If you know the distance, dividing by the economy gives the fuel needed. Multiplying that volume by the pump price gives the fuel cost. The page converts every unit to a common base before calculating, so litres with miles, or gallons with kilometres, work without a separate conversion step. The result is an estimate at a constant economy; cold weather, load, speed, air conditioning and traffic can move the real figure.
Formula
For economy in km per litre, range in km = litres x km/L. Fuel in litres = distance in km / (km/L). Cost = litres x price per litre. An economy in L/100 km converts with km/L = 100 / (L/100 km). One US gallon is 3.785411784 litres and one Imperial gallon is 4.54609 litres.
Worked example
At 7.8 L/100 km, a 50-litre tank holds enough for about 641 km, because 7.8 L/100 km is 12.82 km per litre. A 500 km trip needs 39 litres, and at $1.65 a litre that fuel costs $64.35. At 30 US mpg, 10 US gallons covers 300 miles, or about 483 km.
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Frequently asked questions
Should I use the rated or the real fuel economy?
Use what your vehicle achieves in the conditions you expect. Ratings are measured on a standard cycle, and real consumption is often higher in winter, in stop-and-go traffic or with a heavy load.
Does the range include the reserve?
No. Enter the fuel you are willing to use before refuelling. Running a tank dry can damage the fuel pump, so keep a reserve and use a slightly lower figure than the full tank capacity.
Why does 7.8 L/100 km become 12.82 km per litre?
The two measures are reciprocal. Litres per 100 km says how much fuel a fixed distance uses, while km per litre says how far a fixed volume goes. Dividing 100 by 7.8 gives 12.82.
Can I use this for a trip with several drivers?
Yes. Enter the total distance and the economy of the vehicle, not each driver separately. The estimate covers fuel only and excludes tolls, parking and wear.