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Engine compression ratio calculator

Calculate static compression ratio = (swept volume + clearance volume) ÷ clearance volume.

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Answer

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Calculate static compression ratio = (swept volume + clearance volume) ÷ clearance volume.

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Precision and calculation record
Rounding changes displayed numbers, not the calculation. Text, fractions, matrices and CSV schedules keep their own formatting. Automatic keeps up to 12 significant digits, with money shown to cents where applicable.
Step-by-step calculation
Inputs are substituted below. Each line evaluates the next operation; intermediate values are displayed to 12 significant digits while the calculation uses full precision.
    Saved scenario
    Save the current answer, then change an input to compare. This clears when you leave.
    Formula and assumptions
    Volumes must use one unit and refer to one cylinder. Clearance must include the actual chamber, gasket, deck and piston effects. Static ratio does not predict dynamic compression, knock or fuel requirements.
    Automatic precision shows numbers to 12 significant digits. Thousands separators such as 1,000 are accepted; use a dot for decimals.
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    Use +, −, ×, ÷, parentheses and %. A percentage is divided by 100. This does not change the main tool.
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    Updated 
    Using Engine compression ratio calculator
    Calculate static compression ratio = (swept volume + clearance volume) ÷ clearance volume.
    Volumes must use one unit and refer to one cylinder. Clearance must include the actual chamber, gasket, deck and piston effects. Static ratio does not predict dynamic compression, knock or fuel requirements.
    Next: Engine displacement calculator
    A worked example
    Example inputs: swept volume per cylinder = 500, clearance volume at top dead center = 50. Static compression ratio = 11.
    Before you use the result
    Volumes must use one unit and refer to one cylinder. Clearance must include the actual chamber, gasket, deck and piston effects. Static ratio does not predict dynamic compression, knock or fuel requirements.
    Example results for swept volume per cylinder
    These examples use Clearance volume at top dead center: 50. They are reference calculations, not recommended settings.
    Swept volume per cylinderStatic compression ratio
    2506
    50011
    100021
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    ToolOctopus. “Engine compression ratio calculator.” Updated 2026-09-26. https://tooloctopus.com/engine-compression-ratio-calculator.
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