How this calculator works
Each piston sweeps a cylinder whose cross-sectional area is set by the bore and whose length is the stroke. This tool assumes identical circular cylinders. Displacement counts the swept portion only, not the combustion-chamber clearance volume. Use finished bore dimensions rather than nominal casting dimensions. Cylinder-count mode requires an integer result because a physical engine cannot have a fractional cylinder.
Formula
V = cylinders × pi × bore² × stroke / 4. Per-cylinder swept volume = V/cylinders.
Worked example
Four cylinders each with 100 mm bore and 100 mm stroke displace 3.141592654 L in total. Two cylinders of 100 mm bore with total displacement 1.570796327 L have 100 mm stroke.
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Frequently asked questions
Is displacement the same as combustion-chamber volume?
No. The chamber clearance volume remains above the piston at top dead centre and is excluded.
Does engine speed affect displacement?
No. Displacement is geometric; airflow per unit time also depends on speed and filling.
What about unequal cylinders?
Calculate each bore-and-stroke group separately and add their swept volumes.