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Calculate swept displacement for equal circular cylinders.
Calculators / Automotive / Static compression ratio
Static compression ratio calculator
Calculate a geometric static compression ratio from measured volumes.
On this page
Static compression ratio11: 1
Calculator controls
How to calculate
Calculate a geometric static compression ratio from measured volumes.
Static compression ratio = (swept volume + clearance volume) ÷ clearance volume.
Worked example
Swept volume of one cylinder (cm³): 500; Total clearance volume at TDC (cm³): 50.
Static compression ratio: 11 : 1.
Assumptions and limits
Calculate a geometric static compression ratio from measured volumes. Clearance includes chamber, gasket and piston/deck effects. This does not calculate dynamic compression, safe boost, fuel octane or cylinder pressure.
Results are rounded for display; calculations use unrounded values. Read our calculation methodology.
Understanding the result
Calculate a geometric static compression ratio from measured volumes. Clearance includes chamber, gasket and piston/deck effects. This does not calculate dynamic compression, safe boost, fuel octane or cylinder pressure.
When this tool is useful
Static compression ratio = (swept volume + clearance volume) ÷ clearance volume.
Understanding your inputs
| Input | What to enter |
|---|---|
| Swept volume of one cylinder (cm³) | Enter a number of at least 0.001 and no more than 1000000000000. |
| Total clearance volume at TDC (cm³) | Enter a number of at least 0.001 and no more than 1000000000000. |
Frequently asked questions
Is static compression ratio the same as cylinder pressure?
No. This ratio compares chamber volumes at two piston positions. Actual pressure depends on valve timing, temperature and operating conditions; the figure alone cannot set a safe fuel or boost level.