The displacement of an engine is a measure of its size. It is sometimes known as swept volume.

The displacement of a conventional internal combustion engine is the difference between the volume in the cylinder at top dead centre and the volume at bottom dead centre, multiplied by the number of cylinders in the engine.

Displacement can be calculated from the bore and stroke of the engine:

D  =   (b/2)²  x  π   x  s   x   n

where D is displacement, b is the bore, s is the stroke and n is the number of cylinders.

Displacement is usually expressed in litres (l) or cubic centimetres (cc or cm3) in the UK and Europe, and cubic inches (ci) in the US.

The displacement of a rotary engine is measured in a different way to a normal piston engine, and cannot be directly compared.