Enter the piston diameter and cylinder diameter into the calculator to determine the piston to wall clearance. This calculator can also evaluate any of the variables given the others are known.

Piston To Wall Clearance Formula

The following formula is used to calculate the piston to wall clearance.

PTWC = (PD - CD) / 2

Variables:

  • PTWC is the piston to wall clearance (mm)
  • PD is the piston diameter (mm)
  • CD is the cylinder diameter (mm)

To calculate the piston to wall clearance, subtract the cylinder diameter from the piston diameter, then divide the result by 2. This will give the clearance between the piston and the cylinder wall.

What is a Piston To Wall Clearance?

Piston to wall clearance refers to the small gap between the piston and the cylinder wall in an internal combustion engine. This clearance is crucial for the proper functioning of the engine as it allows for thermal expansion of the piston when the engine is running, prevents the piston from seizing or causing excessive wear, and helps in maintaining a thin layer of lubricating oil. The exact clearance varies depending on the type of engine and the materials used, but it is typically measured in thousandths of an inch.

How to Calculate Piston To Wall Clearance?

The following steps outline how to calculate the Piston To Wall Clearance.


  1. First, determine the piston diameter (PD) in millimeters.
  2. Next, determine the cylinder diameter (CD) in millimeters.
  3. Next, subtract the cylinder diameter (CD) from the piston diameter (PD).
  4. Finally, divide the result by 2 to calculate the Piston To Wall Clearance (PTWC).
  5. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem:

Use the following variables as an example problem to test your knowledge.

piston diameter (PD) = 80 mm

cylinder diameter (CD) = 75 mm