Compression ratio = Total cylinder volume at BDC ÷ Clearance volume at TDC
Compression ratio = (Swept volume + Clearance volume) ÷ Clearance volume
Swept volume = π/4 × bore² × stroke
Clearance volume = volume remaining in the cylinder when the piston is at TDC
Use the same units for all volumes
Example formula: CR = (Vs + Vc) / Vc
Higher compression ratio means more compression of the air-fuel mixture or air charge
Lower compression ratio means less compression of the air-fuel mixture or air charge