📘 AI Summary: Calculate static compression ratio for any engine using bore, stroke, head chamber volume, piston deck height, and gasket thickness. Includes common vintage engine presets.

Compression Ratio Calculator

Tool description: Get accurate static compression ratio for rebuilds or head swaps. Works for any 4-stroke gasoline engine. Lower octane fuel may require ratio under 9.5:1.

Engine Preset (optional):

Bore (mm or inches, specify unit):

Stroke (mm or inches):

Combustion Chamber Volume (cc):

Piston Deck Height (mm, positive if piston below deck):

Head Gasket Compressed Thickness (mm):

Gasket Bore (mm, usually same as bore +0.5):

Understanding Compression Ratio

Static compression ratio = (swept volume + clearance volume) / clearance volume. Higher ratios increase power but require higher octane fuel. Vintage engines typically run 8.0:1 to 9.5:1 on pump gas.

Last updated: May 10, 2026