Engine Compression Ratio Calculator

Calculate your engine compression ratio based on bore, stroke, chamber volume, and head gasket specs.

Engine Dimensions

Bore (mm)

Stroke (mm)

Combustion Chamber Volume (cc)

Gasket Thickness (mm)

Gasket Bore (mm)

Piston Dish/Dome (cc)

Deck Clearance (mm)

Recommended CR by Fuel

87 Octane (Regular)8.5:1 - 9.5:1

91 Octane (Premium)9.5:1 - 10.5:1

93 Octane (Premium+)10.5:1 - 11.5:1

E8511.0:1 - 14.0:1

Race Fuel (110+)13.0:1 - 16.0:1

Understanding Compression Ratio

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

Higher compression means more power and efficiency, but requires higher octane fuel to prevent detonation (knock). Forced induction engines (turbo/supercharged) typically run lower static compression (8.5-9.5:1) since the turbo effectively increases the dynamic compression.

Piston dome volume is positive (reduces clearance volume, increasing CR). Piston dish volume is negative (increases clearance volume, decreasing CR).

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