Engine Displacement Calculator

Because bore is squared in the displacement formula (volume = pi/4 x bore² x stroke x cylinders) while stroke appears only linearly. Cylinder volume tracks the piston's cross-sectional area, which itself grows with the square of the bore diameter, so a 10% increase in bore raises displacement by roughly 21% (1.1² = 1.21), while a 10% increase in stroke raises it by exactly 10%. This is a real engineering consideration during an engine rebuild: boring cylinders out even slightly adds displacement faster than an equivalent stroke change would.

Oversquare (bore wider than stroke, a ratio above 1) generally allows larger valve area relative to displacement and lets the piston complete its stroke in less crankshaft rotation, both of which favor higher safe redline RPM and high-revving power delivery -- common in performance and motorcycle engines. Undersquare (a long stroke relative to bore, a ratio below 1) generally favors low-RPM torque and is more common in diesel and heavy-duty industrial engines, which prioritize low-end pulling power over high-RPM output.

Treat it as a rough sanity-check ballpark, not a real performance figure. It applies a broad historical rule of thumb -- roughly 1 horsepower per 15cc of naturally-aspirated displacement -- averaged loosely across many production engine designs. Real output depends heavily on factors this calculator doesn't know: valve count and size, compression ratio, camshaft timing, cylinder head flow, whether the engine is turbocharged or supercharged, and how it's tuned. Two engines with identical displacement can differ in real horsepower by a wide margin.

Yes -- that's exactly its purpose, and it's the same formula engine builders and machinists use. Enter your measured bore and stroke (choosing millimeters or inches to match your measurement), and the number of cylinders, and the calculator returns total displacement in liters, cubic centimeters, and cubic inches. This is especially useful after an engine rebuild involving an overbore or stroker crankshaft, where the resulting displacement no longer matches the factory-published spec.