Tool
Engine Displacement Calculator
Displacement is the swept volume of the cylinders. In millimeters, cubic centimeters equal π × (bore ÷ 2)² × stroke × cylinder count ÷ 1000. The same geometry in inches is reported as cubic inches.
Displacement
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When to use this calculator
Use it when a manual lists bore and stroke, and you want the swept volume in the two units riders still quote. The page does not add combustion-chamber volume, so it is not a compression-ratio tool.
Cylinders must be a whole number. Overbore is just a larger bore field; enter the finished size, not the stock size plus a note.
One cubic inch is 16.387 cubic centimeters. The calculator uses that constant in both directions so the pair of results stay consistent.
Zero bore, zero stroke, or a blank cylinder count produces a field error.
Worked engines
That parallel twin is 689.6 cc, or 42.08 cubic inches. It is the default because the arithmetic is easy to check by hand.
A large-bore twin lands near 996 cc. If you are comparing a 1000-class badge with the stamped bore and stroke, does the badge match the geometry?
80 mm is 3.150 inches and 68.6 mm is 2.701 inches. Switching the unit control should return the same cubic centimeters within rounding.
Technical questions
Does this include the combustion chamber?
No. Swept volume stops at the piston travel. Compression ratio needs chamber volume as well, and that is a different measurement.
Why divide by 1000 when the inputs are millimeters?
The product π × (bore/2)² × stroke is cubic millimeters. Dividing by 1000 converts that figure to cubic centimeters.
Can I enter a single-cylinder or a four?
Yes. The cylinder field is a multiplier. Enter 1, 2, 3, 4, or another whole count that matches the engine.