Enter the tangential load (lbs), the pitch (1/in), the Lewis factor, and the face width (in) into the Gear Strength Calculator. The calculator will evaluate the Gear Strength. 

Gear Strength Formula

The following formula is used to calculate the Gear Strength. 

GS = TL * P / (F*Y)


  • GS is the Gear Strength (PSI)
  • TL is the tangential load (lbs) 
  • P is the pitch (1/in) 
  • F is the face width (in) 
  • Y is the Lewis Factor

To calculate the gear strength, divide the product of the tangential load and the pitch by the product of the face width and the Lewis Factor.

How to Calculate Gear Strength?

The following steps outline how to calculate the Gear Strength.

  1. First, determine the tangential load (lbs).
  2. Next, determine the pitch (1/in). 
  3. Next, determine the face width (in). 
  4. Next, determine the Lewis Factor.
  5. Next, gather the formula from above = GS = TL * P / (F*Y).
  6. Finally, calculate the Gear Strength.
  7. 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.

tangential load (lbs) = 500

pitch (1/in) = 2

face width (in) = 3

Lewis Factor (dimensionless) = .25

GS = TL * P / (F*Y) =  ?