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Engine Calculators

Compression Ratio Calculator

Static compression ratio from swept and clearance volume, with the head gasket contribution.

Enter values

Negative for a domed piston

Results update as you type.

Result

Compression ratio

8.7 : 1

Swept volume per cylinder
499.56 cc
Total clearance volume
64.875 cc
Head gasket volume
6.971 cc
Deck volume
2.904 cc
Fuel suggestion
Regular is normally fine

About the Compression Ratio Calculator

Static compression ratio from swept and clearance volume, with the head gasket contribution.

Also known as: static compression ratio, cr calculator, chamber volume, engine compression.

How to use this calculator

  1. Enter bore, stroke, combustion chamber volume, head gasket thickness and the other fields.
  2. The result updates instantly as you type — press Calculate (or Enter) at any time.
  3. Review the breakdown shown under the main result.
  4. Use Copy result or Share to save the answer or send a link with your inputs.

Formula

CR = (swept + clearance) ÷ clearance

Worked example

Using the values pre-filled in the calculator above:

  • Bore = 86 mm
  • Stroke = 86 mm
  • Combustion chamber volume = 50 cc
  • Head gasket thickness = 1.2 mm
  • Deck clearance = 0.5 mm
  • Piston dish volume = 5 cc

the calculator returns:

  • Compression ratio: 8.7 : 1
  • Swept volume per cylinder: 499.56 cc
  • Total clearance volume: 64.875 cc
  • Head gasket volume: 6.971 cc