Enter the load, young’s modulus of the rubber, and shape factor into the calculator to determine the rubber deflection.

Rubber Deflection Formula

The following equation is used to calculate the Rubber Deflection.

D =    L /[ Y*(1+2*f^2)]
  • Where D is the rubber deflection in % deflection per inch of thickness (%/in)
  • Y is the young’s modulus (PSI)
  • f is the shape factor
    • The shape factor is calculated by dividing the compressed area by the area that is able to bulge
  • L is the load (PSI)

To calculate the rubber deflection, divide the load by the product of the Young’s modulus times 1 plus 2 times the shape factor squared.

What is Rubber Deflection?


Rubber deflection refers to the load-carrying capacity of a specific material, including the load that is applied and the other forces that may act upon it. It is commonly used when referring to the ability of a material to withstand loading by external forces that are placed upon it.

Tension and compression are two types of external loads that can be applied to a rubber material. Tension refers to a force that pulls in one direction, while compression refers to an opposing force that pushes in another direction. Neither tension nor compression can be adequately explained without also taking into consideration the other factor: strain. Strain is defined as deformation under load, or how much a material is stretching or compressing during tension or compression. The relationship between strain and the amount of force being applied or the distance from the neutral axis plays a significant role in how much deflection will occur within a rubber material.

Deflection can therefore be described as the movement of a material away from its neutral axis due to stress or force, depending on whether tension or compression is being referred to.

Rubber materials typically have high tensile strengths, meaning they do not deflect easily when put under tension, which creates problems for engineers who need to design structures made with rubber materials

How to Calculate Rubber Deflection

To calculate rubber deflection take the shape factor raised to the power of 2, then add 1.

Next, multiply the result from above by the young’s modulus of the rubber.

Finally, divide the load acting on the rubber in PSI by the result from above.