# Compression Ratio

Written by Jerry Ratzlaff on . Posted in Fluid Dynamics

The compression ratio, abbreviated as CR, in an engine is the ratio of the maximum volume to the minimum volume in a cylinder. The equation and calculator below can help find the compression ratio.

 $$\large{ CR = 1 + \frac{\pi}{4} \; \frac { BORE^2 \; STROKE }{CCV \;+\; HGV \;+\; PVD } }$$  Where: $$\large{ CR }$$ = compression ratio $$\large{ BORE }$$ = bore $$\large{ CCV }$$ = combustion chamber volume $$\large{ HGV }$$ = head gasket volume $$\large{ PDV }$$ = piston deck volume $$\large{ STROKE }$$ = stroke length