Texas Pipe and Supply

Leading Distributor of Carbon and Stainless Steel Pipe Since 1918.

Barlow's Formula Calculator

Enter any three numeric values:

psig
in.
in.
psi

Barlow's Formula is Used to Determine:

  • Internal Pressure at Minimum Yield
  • Ultimate Bursting Pressure
  • Maximum Allowable Operating Pressure
  • Mill Hydrostatic Test Pressure

The Formula is Expressed as P=2St/D, Where:

  • P = pressure, psig
  • t = nominal wall thickness, in inches (i.e. .375)
  • D = outside Diameter in inches
  • S = allowable stress in psi, which depends on the pressure being determined utilizing Yield or Tensile depending on what is trying to be determined

For Example:

  • Internal Pressure at Minimum Yield:
    S= SMYS - minimum yield for grade of pipe

Ultimate Bursting Pressure:

  • S = SMTS - minimum tensile strength for grade of pipe

Maximum Allowable Operating Pressure:

  • S = SMYS - reduced by a design factor

Mill Hydrostatic Test Pressure:

  • S = SMYS - reduced by a design factor depending on OD and grade