Enter the wall thickness, outside diameter, and allowable stress into the calculator to determine the pipe pressure rating.

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## Pipe Pressure Rating Formula

The following formula is used to calculate a pipe pressure rating. This is also known as **Barlow’s Formula.**

P = 2 * s * t / D

- Where P is the pressure rating (psig)
- s is the allowable stress (yield stress or tensile) (psi)
- t is the wall thickness (inches)
- D is the outside diameter (inches)

To calculate the pipe pressure rating, multiply two by the allowable stress and the wall thickness, then divide by the outside diameter.

## Definition

**What is a pipe pressure rating? **

A pipe pressure rating is defined as the maximum amount of internal pressure a pipe can handle before it yields under stress.

The pipe pressure rating is dependent on the wall thickness, the overall size (diameter), and allowable tensile or yield stress. The allowable tensile or yield stress is dependent on the type of material the pipe is made of.

## Example Problem

**How to calculate pipe pressure rating? **

The following example problem outlines the steps necessary to calculate a pressure rating.

First, determine the allowable tensile or yield stress of the pipe. For this example, the allowable stress is found to be 500 psi.

Next, determine the wall thickness of the pipe. In this case, the wall thickness is measured to be 2 inches.

Next, determine the outside diameter of the pipe. For this problem, the outside diameter is measured as 10 inches.

Finally, calculate the estimated pipe pressure rating using the formula above:

P = 2 * s * t / D

P = 2 * 500 * 2 / 10

P = 200 psig