Engine Displacement Calculator
Calculate engine displacement in cc, litres and cubic inches from bore, stroke and cylinder count.
How it works
Per cylinder = π/4 × (bore/10)² × (stroke/10) · Displacement = per cylinder × cylinders (bore, stroke in mm)
Displacement is the total volume the pistons sweep in one full cycle. Each cylinder is a short cylinder-shaped volume: its area is π/4 times the bore squared, and multiplying by the stroke gives the swept volume. Converting bore and stroke from millimetres to centimetres (divide by 10) makes the result come out directly in cubic centimetres, which equal cc. Multiplying one cylinder’s volume by the number of cylinders gives the engine’s total displacement, which then converts to litres (÷1,000) or cubic inches (÷16.387).
Worked example
A four-cylinder with an 86 mm bore and 86 mm stroke: per cylinder = π/4 × 8.6² × 8.6 ≈ 499.6 cc. Across four cylinders that is about 1,998 cc — roughly 2.0 litres, or about 121.9 cubic inches.
Frequently asked questions
What is the difference between bore and stroke?
Bore is the diameter of the cylinder; stroke is how far the piston travels between top and bottom. An engine with a bigger bore than stroke is "oversquare" and tends to rev higher; the reverse, "undersquare", favours low-end torque.
Why do quoted litres differ slightly from the exact math?
Manufacturers round to a marketing figure — an engine that calculates to 1,998 cc is sold as "2.0 litre". Small differences between the exact swept volume and the badge are normal.
Does displacement include the combustion chamber?
No. Displacement is only the volume the piston sweeps. The extra space above the piston at top dead centre is the clearance volume, which is used with displacement to work out the compression ratio, not the displacement itself.
Related calculators
Educational estimate. Real-world results vary with conditions, tuning and measurement.