How to use this calculator
- Enter the bore. Enter the cylinder bore diameter.
- Enter the stroke. Enter the piston stroke.
- Enter the cylinder count. Enter the number of cylinders (1 for a single cylinder or pump).
- Read displacement. Read total displacement in cc, litres and cubic inches, plus the bore/stroke ratio.
How it works
Engine displacement is the total volume the pistons sweep. One cylinder sweeps V = (π/4) · bore² · stroke and the engine displacement is that times the number of cylinders. The bore/stroke ratio (bore ÷ stroke) describes the engine's character: oversquare (> 1) breathes well at high RPM, undersquare (< 1) makes low-end torque. Displacement is swept volume only — it does not set the compression ratio, which also depends on the combustion-chamber volume.
The same swept-volume geometry is useful outside engines. For fluid power, combine bore area with pressure in the hydraulic cylinder force calculator, or use pump displacement with RPM and efficiency in the hydraulic pump flow calculator. If the cylinder rod is long or side-loaded, follow the force check with the hydraulic cylinder rod buckling calculator.
Worked example
Verified against the live calculator
An 86 mm bore × 86 mm stroke four-cylinder: each cylinder sweeps
(π/4) × 86² × 86 ≈ 500 cc, so the engine is about
1,998 cc — 2.0 litres, 122 ci. The bore/stroke ratio is 1.0, a
square engine. The calculator returns exactly this.
Frequently asked questions
How do you calculate engine displacement from bore and stroke?
Displacement = (π/4) × bore² × stroke × number of cylinders. The (π/4)·bore²·stroke part is the swept volume of one cylinder; multiply by the cylinder count for the total.
How do I convert between cc, litres and cubic inches?
1,000 cc = 1 litre, and 1 cubic inch = 16.387 cc. The calculator shows all three at once.
What is the bore/stroke ratio?
Bore ÷ stroke. Above 1.0 is oversquare (bore wider than the stroke) — it favours high RPM; below 1.0 is undersquare (long stroke) — it favours low-end torque; 1.0 is square.
Does displacement include the compression ratio?
No. Displacement is only the swept volume. The compression ratio also depends on the combustion-chamber (clearance) volume, which this does not include.
Can I use this for a hydraulic cylinder or pump?
Yes — set cylinders to 1. The same (π/4)·bore²·stroke gives the swept (displaced) volume per stroke of a cylinder or pump.
Does it work in metric and imperial?
Yes — enter bore and stroke in mm or inches; displacement is shown in cc, litres and cubic inches.
Method & assumptions
- Displacement is swept volume only; the compression ratio additionally needs the combustion-chamber (clearance) volume.
- The same formula gives a hydraulic cylinder or pump's swept volume per stroke; use one cylinder, then check force or flow with the hydraulic tools linked above.