Compression Ratio Calculator
Calculate static compression ratio from bore, stroke, chamber volume, piston dome or dish, deck clearance and head gasket dimensions.
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Cam timing, boost, altitude, fuel octane, quench and ignition timing can change real detonation margin.
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Test changes to chamber volume and piston dome/dish without changing your main inputs.
Calculate your baseline first
Static compression ratio is (swept volume + clearance volume) / clearance volume. Swept volume comes from bore and stroke; clearance volume includes chamber, gasket, deck and piston dome or dish volume.
In this tool, negative piston volume means a dish or valve relief that adds clearance volume. Positive piston volume means a dome that reduces clearance volume.
No. Static ratio is only one input. Camshaft timing, dynamic compression, combustion chamber shape, quench, intake temperature, boost, ignition timing and fuel quality all affect knock margin.
Results are estimates generated locally in your browser from standard geometry formulas. They are for informational engine-planning use only and are not a guarantee of safe tuning, fuel compatibility, emissions compliance or engine durability. Verify measurements and consult a qualified engine builder before machining, tuning or purchasing parts.
