Compression Ratio Calculator

Your details

Total number of cylinders in the engine (used for total displacement only).
Cylinder bore diameter (inner diameter of the cylinder).
mm
Distance the piston travels from bottom dead center (BDC) to top dead center (TDC).
mm
Volume of the combustion chamber in the cylinder head at TDC. Measure with a burette or get the value from the head manufacturer.
cc
Compressed thickness of the head gasket. Most performance gaskets are 0.040 in (1.0 mm).
mm
Inner diameter of the head gasket opening. Usually slightly larger than the cylinder bore.
mm
Distance between the piston crown and the deck surface of the block at TDC. Positive = piston below deck (typical). Zero = piston flush.
mm
Flat-top pistons contribute no additional volume. Dish pistons add volume; dome pistons subtract it.
Leave 0 for flat-top. For dish, enter the dish volume (adds to Vc). For dome, enter the dome volume (subtracts from Vc).
cc
Dynamic CR accounts for the intake valve closing (IVC) angle after BDC. The actual compression stroke is shorter than the full stroke, so the effective CR is lower.
Static compression ratioPerformance street
10.35:1

(Vd + Vc) / Vc

Per-cylinder displacement716.7cc
Total engine displacement5,733cc
Total displacement (L)5.73L
Compressed volume (Vc)76.65cc
10.35 :1
Low/diesel<8Mild street8-10Performance10-12High perf12-14Race/forced14+

Compression ratio: 10.35:1

  • A static CR of 10.35:1 is in the mild street range suitable for pump premium fuel.
  • 91-93 octane premium fuel is recommended.
  • Total engine displacement is 5.73 L (350 ci).

Next stepTo raise the CR, reduce combustion chamber volume, decrease deck clearance, or switch to dome-top pistons. To lower it, mill the block/head less aggressively or add a thicker head gasket.

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