Engine compression ratio from one cylinder's swept volume and chamber volume.
| CR | – |
Use this calculator for a static CR check when you know displacement per cylinder and the volume at top dead centre.
CR = (swept + chamber) / chamber. 400 ml swept and 40 ml chamber is 11:1. One millilitre equals one cubic centimetre. Volumes can be millilitres (ml) or fluid ounces (fl oz); both sides use the same unit so the ratio is unchanged. Swept volume is π/4 × bore² × stroke if you compute it aside. Gauge PSI from CR needs fuel and efficiency and is not here.
Swept: Displacement of one cylinder. Enter ml or fl oz (1 ml = 1 cc).
Chamber: Combustion-chamber volume at TDC, not zero.
CR: Static compression ratio, dimensionless.
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