Calculators · Engine
Engine displacement and bore/stroke calculator
Engine displacement is the total volume swept by all pistons in one full stroke. It is the single most quoted engine figure, and it follows directly from three measurements: cylinder bore, piston stroke and the number of cylinders. The calculators below work in both directions — from bore and stroke to displacement, or from a known displacement back to the bore or stroke — and classify the engine by its bore-to-stroke ratio.
Displacement from bore, stroke and cylinders
Calculates the swept volume of one cylinder and of the whole engine. Use it when you know the bore and stroke from a specification sheet or measurement and want the engine size in cc, litres or cubic inches.
V_cyl = π/4 × bore² × stroke V_total = V_cyl × cylinders
Bore from displacement and stroke
Works backwards from a known engine size and stroke to the cylinder bore. Handy when a manufacturer quotes displacement and stroke but not the bore, or when planning an overbore.
bore = √( 4 × (V_total / cylinders) / (π × stroke) )
Stroke from displacement and bore
Finds the stroke that gives a known displacement with a known bore. Engine builders use this when choosing a stroker crankshaft to reach a target capacity.
stroke = (V_total / cylinders) / (π/4 × bore²)
Bore-to-stroke ratio
Divides bore by stroke and classifies the engine as oversquare, square or undersquare. Oversquare engines (ratio above 1) usually rev higher; undersquare engines favour low-speed torque and are common in diesels.
ratio = bore / stroke
Worked example: a 2.0-litre inline-four
- Bore 86 mm, stroke 86 mm, 4 cylinders — a common square layout.
- Area of one bore: π/4 × 86² = 5,808.8 mm².
- Volume of one cylinder: 5,808.8 × 86 = 499,555 mm³ = 499.6 cc.
- Total: 499.6 × 4 = 1,998 cc, sold as a 2.0-litre engine.
- Bore/stroke ratio: 86 / 86 = 1.00, so the engine is square.
Bore and stroke of well-known engines
| Engine | Bore × stroke | Displacement | Layout |
|---|---|---|---|
| Honda K20A | 86 × 86 mm | 1,998 cc | Square |
| Honda F20C | 87 × 84 mm | 1,997 cc | Oversquare |
| Toyota 2JZ-GTE | 86 × 86 mm | 2,997 cc | Square |
| BMW N54 | 84 × 89.6 mm | 2,979 cc | Undersquare |
| Ford 5.0 Coyote (2011) | 92.2 × 92.7 mm | 4,951 cc | Square |
| Cummins 6BT 5.9 | 102 × 120 mm | 5,883 cc | Undersquare |
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About these results
Results are theoretical estimates from standard engineering formulas. Real-world figures depend on conditions these formulas do not capture. Always follow the manufacturer's specifications for maintenance, loading and safety decisions.
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