3 Calculators
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Vehicle figures worked from your own numbers, including fuel economy, power to weight ratio and engine displacement.
These calculators work out the numbers that describe a vehicle from figures you supply: fuel economy from distance and fuel used, power-to-weight ratio from horsepower or kilowatts and the vehicle’s weight, and engine displacement from bore, stroke and the number of cylinders. Each page shows the formula and keeps the units visible, because car figures arrive in a mix of US and metric units.
Fuel economy is shown both ways it is quoted: miles per US gallon, and litres per 100 kilometres, which runs the other way round, so a lower figure is better. The conversion uses the exact US gallon of 3.785411784 litres and the international mile of 1.609344 kilometres.
Displacement is the swept volume of the cylinders: the area of the bore times the stroke times the number of cylinders. It is reported in cubic centimetres, litres and cubic inches, the three units manufacturers use.
Start here
- What mileage am I really getting?
- Note the trip distance and the fuel added at the next fill-up, then enter both in the MPG calculator.Miles per Gallon Calculator (MPG and L/100 km)
- How big is an engine with an 86 mm bore and 86 mm stroke?
- Enter the bore, stroke and cylinder count in the engine displacement calculator.Engine Displacement Calculator (Bore and Stroke to cc, Litres and Cubic Inches)
How these calculators fit together
Fuel economy
The MPG calculator divides distance by fuel used and converts between miles per gallon and litres per 100 kilometres, using the fill-up method: fill the tank, drive, then fill again and note the fuel added.
Engine and performance
The power-to-weight calculator divides power by mass and reports it per tonne and per pound. The engine displacement calculator works the swept volume from bore, stroke and cylinder count.
Power to Weight Ratio Calculator (hp per Tonne and lb per hp)Engine Displacement Calculator (Bore and Stroke to cc, Litres and Cubic Inches)
What these tools leave out
- Measured fuel economy depends on the fill-up being consistent. A single tank can be off by several percent.
- Power figures differ by how they were measured, at the crank or at the wheels; the calculators use the figure you enter.
- Nothing here estimates ownership costs or loan payments; those are in the finance calculators.
All Calculators
Works out engine displacement from bore, stroke and the number of cylinders, in cubic centimetres, litres and cubic inches, with the swept volume per cylinder and the bore-to-stroke ratio.
Works out fuel economy from distance driven and fuel used, in miles per US gallon, litres per 100 km, km per litre and gallons per 100 miles, with the fuel cost per mile.
Works out a vehicle's power-to-weight ratio in horsepower and kilowatts per tonne and horsepower per pound, and its weight-to-power ratio in pounds per horsepower and kilograms per kilowatt.