Compression Ratio / Displacement Calculator
Quickly and accurately calculate engine compression ratio and total displacement.
← Go to Component Fit Calculator
| Bore: |
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| Stroke: |
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| Combustion Chamber Volume: |
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| Piston Dome / Dish: Use (-) for Dome and (+) for Dish. |
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| Deck Clearance: |
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| Compressed Gasket Thickness: |
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| Number of Cylinders: | |
| Compression Ratio: | |
| Total Displacement (in³): | |
| Total Displacement (cc): | |
Compression Ratio – Definition and Calculation
The compression ratio (CR) is one of the most critical parameters in internal combustion engines. It describes how much the cylinder volume changes during the piston's movement from bottom dead center to top dead center. It is defined as:
Or in symbols:
A higher compression ratio improves thermal efficiency and power output but also increases the risk of detonation. Therefore, optimizing CR requires considering the fuel’s octane rating, cooling efficiency, and ignition timing.
Typical values:
Gasoline engines: 9:1 – 12:1
Diesel engines: 14:1 – 22:1
This calculator allows you to precisely determine compression ratio by entering geometric engine parameters such as bore, stroke, chamber volume, piston dome/dish volume, deck clearance, and gasket thickness. The results can be used to evaluate component changes and optimize engine performance, fuel efficiency, and durability.
Keywords: compression ratio, swept volume, clearance volume, engine calculator, dome piston, dish piston, performance, tuning, engine tech