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Cylinder Compression Geometry
Compute swept volume, static compression ratio and effective stroke from engine geometry.
- Formula & worked example
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Calculator inputs
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How to use this calculator
- Enter the known values in the units shown. Results update as you type.
- Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
- Use the worked example to check the method. Reset restores the starting fields.
Private by default
Inputs and results stay in this browser tab. Bookify does not upload or store the values you enter.
Formula and method
Four cylinders with 100 mm bore and stroke displace about 3,141.59 cm³ in total.
Compression ratio = (swept volume + compressed volume) / compressed volume
Worked example
Enter these known values and leave the other values blank.
- Number of cylinders
- 4
- Bore diameter (b)
- 100 mm
- Piston stroke (s)
- 100 mm
- Head gasket thickness (t)
- 1 mm
- Gasket bore (g)
- 100 mm
- Deck clearance (c)
- 0 mm
- Combustion chamber volume
- 100 cc
- Piston volume
- 0 cc
- Compressed volume
- 107.85 cc
- Displacement volume
- 785.4 cc
- Engine volume
- 3141.6 cc
- Compression ratio
- 8.282 **: 1**
Assumptions and limitations
- All cylinder volumes use circular bore geometry. Piston volume is signed: use the convention consistent with the supplied chamber volume. Dynamic compression uses a rigid slider-crank geometric model, not a cylinder-pressure prediction. Positive compressed volume and valid connecting-rod geometry are required.
Common questions
What does this estimate assume?
All cylinder volumes use circular bore geometry. Piston volume is signed: use the convention consistent with the supplied chamber volume. Dynamic compression uses a rigid slider-crank geometric model, not a cylinder-pressure prediction. Positive compressed volume and valid connecting-rod geometry are required.
Can I find a missing input?
Clear the unknown field and enter compatible known values. The controls retain supported inverse calculations, while rounded counts and one-way outputs stay directional.
References
Cylinder stroke, gasket bore and combined compressed volume are positive; chamber volume is nonnegative. A rod at least as long as the crank radius keeps the rigid slider-crank geometry real for every angle.
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