Displacement from Bore and Stroke Calculator
Engine displacement is the total swept volume of all pistons through one full stroke, and it is the primary measure of an engine's size. This calculator computes displacement from cylinder bore diameter and stroke length using the standard geometric formula V = (pi/4) * bore^2 * stroke * cylinders. Enter bore and stroke in inches to get displacement in cubic inches, cubic centimeters, and liters simultaneously. This is the formula used by engine builders, machinists, and racing rules administrators to verify engine displacement for class eligibility.
Displacement formula
Displacement (ci) = (pi / 4) * bore^2 * stroke * cylinders Displacement (cc) = ci * 16.387064 Displacement (L) = cc / 1000
All dimensions in inches give cubic inches. Multiply by 16.387064 for cc (exact per NIST). For a classic 350 V8 with 4.000 in bore and 3.480 in stroke: (pi/4) * 16 * 3.48 * 8 = 350.0 ci = 5,735 cc = 5.735 L.
Overbore effects on displacement
- Boring a 350 ci V8 (4.000 in bore) 0.030 in over (4.030 in bore) increases displacement to approximately 355.6 ci.
- Stroke increases raise displacement more efficiently than bore increases per incremental change, because displacement scales linearly with stroke but with the square of bore.
- However, wider bores allow larger valves and better breathing, making over-bore popular for high-revving performance engines.
Frequently asked questions
What is the displacement formula?
Displacement = (pi/4) * bore^2 * stroke * number of cylinders. In inches, this gives cubic inches; multiply by 16.387 for cubic centimeters. This formula calculates the swept volume of all pistons combined over one stroke.
What is the difference between bore and stroke?
Bore is the diameter of the cylinder. Stroke is how far the piston travels from bottom dead center (BDC) to top dead center (TDC). Engines with bore greater than stroke are called over-square and tend to rev higher; engines with stroke greater than bore are under-square and produce more torque at lower RPM.
How does bore and stroke affect power characteristics?
Increasing bore (wider cylinder) allows larger valves and improves breathing at high RPM, producing peak power higher in the rev range. Increasing stroke (longer piston travel) increases torque at lower RPM but limits maximum RPM due to higher piston speed. Diesel engines are typically under-square; high-revving sports engines are over-square.
What is mean piston speed?
Mean piston speed = 2 * stroke * RPM / 12 (feet per minute). Most passenger car engines run 2,000-4,000 ft/min at peak power. Racing engines may reach 5,000-6,000 ft/min. Piston speed is a key durability limitation: higher piston speed increases ring and cylinder wear.
How do I convert cubic inches to liters?
Multiply cubic inches by 0.016387. For example, 350 ci * 0.016387 = 5.74 liters (5.7L). Or divide cubic centimeters by 1000.
Official sources
- SAE International: sae.org - engine geometry and displacement standards.
- NIST: nist.gov - unit conversion factors (1 in = 25.4 mm).
Reviewed by the CalculatorHub team, edited by James Graham, 15 June 2026. See our methodology.