Engine Compression Calculator
Calculate an engine's static compression ratio using cylinder dimensions, piston deck clearance, gasket size, and combustion-chamber volume.
Enter engine dimensions
Result
Enter the engine dimensions to calculate compression ratio.
Compression ratio basics
Compression ratio compares total cylinder volume at bottom dead center with the remaining volume at top dead center.
Piston volume signs
Enter a dish as a positive volume because it adds clearance. Enter a dome as a negative volume because it removes clearance.
Measure carefully
Small changes in gasket thickness, deck clearance, or chamber volume can noticeably change the final ratio.
Frequently asked questions
What formula does this calculator use?
Compression ratio equals swept volume plus clearance volume, divided by clearance volume.
What is swept volume?
It is the volume displaced by one piston as it travels from top dead center to bottom dead center.
Should a piston dome be negative?
Yes. A dome reduces clearance volume, so enter its volume as a negative number. A piston dish is positive.
Is this the same as a compression test?
No. This calculator estimates geometric compression ratio. A compression test measures actual cylinder pressure in psi or bar.
Results are estimates generated locally in your browser using standard formulas and general assumptions. They are for informational purposes only and may not reflect your specific circumstances. VisionVix accepts no liability for decisions based on this tool's output.
