Calculate Piston Size or Engine Displacement
The Engine Displacement Calculator is a free web tool that instantly computes engine displacement (in cc) based on bore, stroke, and cylinder count. It also supports reverse calculations—if you already know the displacement, you can calculate either the bore or stroke. This is especially useful when working with incomplete engine specs or during custom tuning and maintenance. The tool is mobile-friendly and responsive, making it easy to use on any device. Whether you're designing an engine, verifying modifications, or exploring mechanical relationships, it's built for professionals and hobbyists alike.
Instantly calculate engine displacement or piston size from bore, stroke, and cylinder count. Reverse calculations supported. Free, easy to use, and no sign-up needed. Works on any device.
Engine displacement input
How to Use Engine Displacement Calculator
- Enter any two of the following: bore (mm), stroke (mm), or displacement (cc).
- Select the number of cylinders from the dropdown (default is 1).
- Click the 'Calc' button next to the missing value to calculate it automatically.
- Calculations can be performed in any direction (e.g., derive bore from displacement).
- If any required value is zero or missing, an error message will be displayed.
What is Engine Displacement?
Engine displacement, also called engine capacity or engine size, is the total volume of air-fuel mixture an engine moves in one complete cycle. It is usually measured in cc (cubic centimeters), liters, or sometimes cubic inches.
Displacement is calculated from the bore (the diameter of the cylinder), the stroke (the length the piston travels), and the number of cylinders. The basic formula is: Displacement = π × (bore ÷ 2)^2 × stroke × number of cylinders.
- D [cc] : Displacement (cc)
- R [mm] : Bore (mm)
- L [mm] : Stroke (mm)
- n : Number of cylinders
For example, if an engine has a bore of 75mm, a stroke of 90mm, and 4 cylinders, its total displacement would be approximately 1,590 cc.
A larger displacement usually means more power, but overall performance also depends on design factors like combustion efficiency and engine tuning.
In summary, engine displacement is a key value for understanding engine size and comparing engine performance.
Why Increasing Engine Displacement Boosts Power
When engine displacement increases, the amount of air the engine can draw in at once also increases. With more air available, a proportional amount of fuel can be added, resulting in greater combustion energy and improved power output.
For example, even with the same engine design, a larger displacement typically means more energy is generated per combustion cycle, leading to increased torque and power.
However, since air and fuel must be mixed at an appropriate ratio, adjustments to the carburetor or fuel injectors are usually necessary after increasing displacement.
That said, a larger displacement does not automatically mean higher speed. Factors such as vehicle weight, fuel efficiency, and engine RPM characteristics also play important roles in overall performance.
Go to the Torque, Power, and RPM Calculator
If you're working with internal combustion engines, engine displacement can be a useful reference for torque and power. You can easily calculate displacement with our dedicated tool below.