# Compression Ratio

Written by Jerry Ratzlaff on . Posted in Fluid Dynamics

The compression ratio 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.

### Compression Ratio Formula

$$\large{ CR = 1 + \frac{\pi}{4} * \frac { BORE^2 * STROKE } {CCV + HGV + PVD } }$$

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