Engine Displacement Calculator

How it is calculated

The tool treats each cylinder as a short cylinder of diameter bore and length stroke. Both are entered in millimetres and converted to centimetres, so the volume of one cylinder is V1 = (π/4) × bore² × stroke in cubic centimetres. The engine total is V = V1 × cylinders, and litres are V / 1000. Total is shown as a whole number of cc, litres with two decimals and the per-cylinder figure with one decimal. The total is calculated from the unrounded per-cylinder volume, so multiplying the rounded per-cylinder number by the cylinder count can differ by a cc or two. Bore, stroke and cylinder count must all be above zero. It measures swept volume only, not the combustion chamber or compression ratio.

Common mistakes

• Entering bore and stroke in centimetres or inches. The fields are in millimetres, so 8.6 instead of 86 would make the result a thousand times too small.
• Entering the piston radius or the cylinder wall thickness instead of the bore, which is the full cylinder diameter.
• Using the connecting rod length or the crankshaft throw as the stroke. The stroke is the piston travel, which is twice the crank throw.
• Entering cubic inches thinking the result will match, or comparing with a cubic-inch figure. Convert separately: the output here is cc and litres.
• Expecting the marketing figure to match exactly. Makers round, for example 1,998 cc is sold as 2.0 L, so small differences are normal.