Compression Ratio Calculator

Inputs

View results
Cylinder bore diameter.
mm
Piston stroke.
mm
Cylinder count for total displacement.
Combustion chamber volume at TDC.
cm³
Positive for dish or valve reliefs. Negative for dome volume.
cm³
Positive if the piston is below deck at TDC. Negative for pop-up above deck.
mm
Head gasket bore diameter.
mm
Compressed head gasket thickness.
mm

Results

Default result
Edit inputs
Compression ratio
8.82
Pass

Static ratio only; dynamic compression depends on intake valve closing and cam timing.

Also computed

Clearance volume 63.85 cm³

Chamber + piston + gasket + deck.

Swept volume / cylinder 499.6 cm³

Total displacement 1,998 cm³

Gasket volume 5.945 cm³

Deck volume 2.904 cm³

Method notes 2 notes
  • Positive piston volume means a dish or valve relief. Enter a dome as a negative volume.
  • This is static geometric compression ratio. Octane requirement depends on cam timing, chamber shape, fuel, boost, temperature and tuning.

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