Engine Capacity and Compression Calculator

Calculate the deck height required or head volume needed in the combustion chambers to achieve a desired compression ratio. Play with it!

Engine Item
MM Inches Measurement
Engine Bore
Engine Stroke
Deck Height
Combustion Chamber CCs
Compression Ratio
Number of cylinders
Engine Size:


Enter value, then click HERE to calculate.

MM Inch Fraction


The change in horsepower due to the change in compression ratio is relative but not directly proportional. That is to say that a change from 8:1 to 9:1 will give you a larger increase than would the change from 13:1 to 14:1.
I seem to recall for every one point change around 7:1, that is the change from 7:1 to 8:1, would be slightly more than a 3% power increase. Once you get up to around 13:1, that same one point change is only good for about a 1.5% power increase.
The rule of thumb for the compression ratios run in most street engines is: for every point change in the compression ratio your power output will change by 2%. Using this rule of thumb on an engine that produces 100hp, every 1 point change in compression ratio will result in approx. a 2hp change in output.

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