This Pipe Wall Chart specifies the thickness of a pipe's wall. It is not a precise measurement but a guideline based on a wall thickness formula. Two pipes of the same diameter may have different schedules, implying that their wall thickness is different. Tubing wall thickness is measured in inches (. 0035′′) or by standard gauge ranging from 7 (heaviest) to 22 (lightest), which relates to a range of wall thicknesses. As the Pipe Wall Chart on the right shows, not all 12 Gauges allow a thickness between 0.101 and 0.111. A Schedule 40 pipe 4 inches (100 mm) in diameter has an outside diameter of 4.500 inches (114.30 mm), a wall thickness of 0.237 inches (6.02 mm), and a bore of 4.026 inches (102.26 mm).
