Compression Ratio Calculator

This calculator will compute static compression ratio, commonly just called compression ratio. An engine's compressio ratio is the ratio of its cylinder volume at top of piston travel (Top Dead Center) to the bottom of piston travel (Bottom Dead Center).

Compression (static) Calculator inch metric
Bore in
Stroke in
Cylinder Head Chamber Volume cc
Piston Dome Volume** cc
Head Gasket Volume** cc
Deck Clearance** in
Compression Ratio 0.00 :1

**Some Notes:

Piston Dome Volume: enter a positive (+) number for dished pistons and a negative (-) number for domed pistons. For dished (or flatop with valve reliefs) the cc volume entered is the amount of volume held by the piston top (dish and valve reliefs combined). It is a positive (+) number because it adds to chamber volume. For domed pistons, the cc volume entered is the total amount of volume above the piston flat (dome). It is a negative (-) number for domed pistons because it subtracts from the chamber volume.

Head Gasket Volume: for most engines about 6-9ccs

Deck Clearance: enter a positive (+) number when piston is below deck. Enter a negative (-) number if piston rises above deck. Note it is very unusual for piston to rise above the deck.