Compression Ratio Calculator
Liguori Drag Racing / Engine calculators
Compression Ratio Calculator
Calculate static engine compression ratio from measured bore, stroke, chamber volume, piston crown, compressed head gasket and deck clearance. Volumes are per cylinder.
Enter your own measurements. No factory specifications are assumed.
Calculation method & limitations
Swept volume = π × bore² × stroke ÷ 4. Gasket volume uses gasket bore and compressed thickness. Deck volume uses engine bore and signed deck clearance. Clearance volume = chamber + gasket + deck + signed piston crown volume. Dish and valve reliefs add volume; a dome subtracts it. Static ratio is unaffected by cylinder count; cylinder count changes total displacement. This does not calculate dynamic compression or determine a safe ratio for a fuel, boost level or tune.