S = wall thickness (mm) | S = pipe serial (-) Σ s = hoop stress (N/mm 2) | PN = normal pressure (bar) | da = external pipe diameter (mm) ISO 161-1 uses the following formula to calculate the wall thickness of pipe: It is important to understand the different elements of a bend in order to make accurate calculations. This radius will vary depending on the outside diameter of the tube, the wall thickness, and the angle at which the tube is to be bent. When calculating bend allowances to determine the cut length of HDPE conduit or PVC pipe, one must calculate from the center line radius (CLR) of the finished, bent pipe. An inexpensive scientific calculator and an angle finder are the only additional tools required. Using just a few mathematical formulas allows you to properly calculate a bend of nearly any angle.
