About this tool
Engine Displacement Calculator is a free, in-browser tool that works out an engine's total swept volume from the cylinder bore, the piston stroke and the number of cylinders. Enter bore and stroke in millimetres or inches — the unit selector converts inches to millimetres for you. Nothing is uploaded; the math runs entirely in your browser.
The volume of one cylinder is (π ÷ 4) × bore² × stroke, giving cubic millimetres when bore and stroke are in mm. Multiplying by the cylinder count and dividing by 1000 gives total displacement in cubic centimetres (cc); dividing cc by 1000 gives liters and dividing by 16.387 gives cubic inches (CID). The bore/stroke ratio is simply bore ÷ stroke.
Use it to confirm an engine's advertised size, size a rebuild with an overbore, or compare designs. A bore/stroke ratio above 1 is oversquare (a short-stroke, high-revving layout), below 1 is undersquare (long-stroke, torque-biased), and exactly 1 is square.