Steel pipe strength is defined by the minimum yield strength of the steel, the diameter of the pipe, and the wall thickness. This will determine the maximum possible allowable operating pressure for the pipe. Typical specified minimum yield strengths (SMYS) for pipe steel range from 35,000 to 65,000 pounds per square inch at yield.
This SMYS for a particular steel is certified to be the minimum tensile stress on a finite element of the pipe wall required to produce permanent deformation, which means that when subjected to lower tensile stresses, the pipe wall will not incur permanent deformation. Operating yield stresses are limited by code to 40%, 50%, 60%, or 72% of the SMYS depending upon the potential density of human population near the pipeline. In distribution, bias for sufficient wall thickness to reduce risk of puncture typically determines wall thickness rather than the above design factors.
| Class location | Density - buildings within 220 yards of pipeline per mile | Design Factor |
| I | Fewer than 20 houses | 72% |
| II | Fewer than 46 but greater than 10 houses | 60% |
| III | Greater than 46 houses or pipeline within 100 yards of building or place of assembly occupied frequently | 50% |
| IV | Buildings are greater than 4 stories are prevalent | 40% |