Compression Ratio Calculator

Calculate engine compression ratio from cylinder volume, clearance volume, and piston dome/dish volume.

Swept Volume per Cylinder (cc)

Clearance Volume (cc)

Head Gasket Volume (cc)

Piston Dish (+ dish / - dome) (cc)

How It Works

Enter swept volume (displacement per cylinder), clearance volume, head gasket volume, and piston dish/dome volume. The calculator computes the static compression ratio.

Formula

CR = (Swept Volume + Clearance Volume) / Clearance Volume

Frequently Asked Questions

What is compression ratio?

Compression ratio is the ratio of the maximum to minimum volume in an engine cylinder. Higher compression ratios generally improve thermal efficiency and power output but require higher octane fuel.

What is a good compression ratio?

Street engines typically run 8:1 to 10.5:1. Performance engines run 11:1 to 13:1. Race engines can exceed 14:1 but require race fuel.