Enter the box section modulus and the pin section modulus into the calculator to determine the bending strength ratio.

Bending Strength Ratio Formula

The following equation is used to calculate the Bending Strength Ratio.


  • Where BSR is the bending strength ratio
  • BSM is the box section modulus
  • PSM is the pin section modulus

To calculate the bending strength ratio, simply divide the box section modulus by the pin section modulus.

What is a Bending Strength Ratio?


A bending strength ratio is a term most often used in the oil and gas industry to indicate the ratio of the box section modulus to the pint section modulus of a given connection.

How to Calculate Bending Strength Ratio?

Example Problem:

The following example outlines the steps and information needed to calculate Bending Strength Ratio.

First, determine the box section modulus. In this example, the box section modulus is 500 GPa.

Next, determine the pin section modulus. The modulus at the pin is measured to be 400 GPa.

Finally, calculate the bending strength ratio using the formula above:


BSR = 500/400

BSR = 1.25