Compression ratio calculator

Combine swept volume and the entered clearance volumes to calculate a theoretical static compression ratio.

Positive for a dish, negative for a dome
Use a negative value when the piston is above the deck
Static compression ratioEnter values to calculate

Every clearance volume belongs in the denominator

The chamber, gasket, deck clearance and piston dish add to clearance volume. Enter a dome as a negative piston volume because it displaces space from that total.

Static ratio is not cylinder pressure

Cam timing, sealing, altitude, temperature and cranking conditions affect dynamic and measured pressure. This page only evaluates the geometric static ratio.

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