Engine Displacement Calculator
Calculate engine displacement from bore, stroke and cylinder count, or solve the bore or stroke required for a target displacement.
Engine displacement formula
Engine displacement is the total swept volume of every piston. Bore is the cylinder diameter, stroke is the piston travel, and the cylinder count multiplies the swept volume of one cylinder.
Displacement = π ÷ 4 × bore² × stroke × cylinders
Required bore = √[4 × target displacement ÷ (π × stroke × cylinders)]
Required stroke = 4 × target displacement ÷ (π × bore² × cylinders)
The calculator performs the geometry in millimeters and converts the result using exactly 1 cubic inch = 16.387064 cubic centimeters. Nominal engine labels are often rounded, so a measured result such as 1,997.42 cc may be marketed as a 2.0-liter engine.
Example
A four-cylinder engine with an 85 mm bore and 88 mm stroke has approximately 1,997.42 cc, 1.997 liters or 121.89 cubic inches of total swept volume. A 0.5 mm overbore increases the diameter, so its effect is squared in the volume formula.
Oversquare, square and undersquare
An engine is oversquare when bore is larger than stroke, undersquare when stroke is larger than bore, and approximately square when the two dimensions are within 1%. This geometric description does not by itself determine torque, power, efficiency, reliability or safe RPM.
Important limits
This tool calculates nominal swept volume. It does not include combustion-chamber volume, head-gasket volume, piston dome or dish, deck clearance, wear, machining tolerance or thermal expansion. Those quantities matter for compression ratio, not basic displacement. Cubic centimeters cannot be converted directly to horsepower because power also depends on airflow, combustion, volumetric efficiency, RPM, boost and many other design factors.
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