Pipe Schedule Chart — Sizes & Weight

Pipe schedule is a dimensionless number that designates the wall thickness of a pipe for a given nominal pipe size (NPS). Higher schedule numbers mean thicker walls and higher pressure ratings. The schedule number was originally defined as the approximate value of 1000 × P/S, where P is the internal working pressure in psi and S is the allowable stress in psi. Common schedules include 5, 10, 20, 30, 40, 60, 80, 100, 120, 140, and 160. Schedule 40 and Schedule 80 are the most widely stocked and specified.

Schedule 40 and Schedule 80 pipe have the same outside diameter for a given nominal pipe size, but Schedule 80 has a thicker wall. For example, 2-inch NPS pipe has an OD of 2.375 inches in both schedules, but Schedule 40 has a 0.154-inch wall (ID 2.067 inches) while Schedule 80 has a 0.218-inch wall (ID 1.939 inches). The thicker wall of Schedule 80 gives it a higher pressure rating but reduces flow capacity and increases weight per foot.

No. For pipe sizes NPS 1/8 through NPS 12, the nominal pipe size does not equal the outside diameter. For example, NPS 1/2 pipe has an actual OD of 0.840 inches, and NPS 1 pipe has an actual OD of 1.315 inches. This is because the nominal sizes were originally based on approximate inside diameters. For NPS 14 and larger, the nominal size does equal the outside diameter (14-inch NPS pipe has a 14.000-inch OD).

STD (Standard), XS (Extra Strong), and XXS (Double Extra Strong) are traditional wall thickness designations that predate the schedule numbering system. For NPS 1/8 through NPS 10, STD is identical to Schedule 40. For NPS 1/8 through NPS 8, XS is identical to Schedule 80. For larger sizes, STD has a 3/8-inch wall and XS has a 1/2-inch wall — these do NOT correspond to Schedule 40 and 80 in larger sizes. XXS is the heaviest standard wall thickness available and does not correspond to any schedule number.

Inside diameter (ID) equals the outside diameter (OD) minus twice the wall thickness: ID = OD − 2 × wall thickness. For example, 4-inch NPS Schedule 40 pipe has OD = 4.500 inches and wall thickness = 0.237 inches, so ID = 4.500 − 2 × 0.237 = 4.026 inches. The table on this page shows ID already calculated for every pipe size and schedule combination.

This chart covers carbon steel pipe per ASME B36.10M. Stainless steel pipe dimensions are defined by ASME B36.19M, which uses schedule suffixes with an “S” (5S, 10S, 40S, 80S). For NPS 12 and smaller, Schedule 40S wall thicknesses are identical to Schedule 40 in B36.10M, and Schedule 80S matches Schedule 80. The outside diameters are the same across both standards for all sizes. The key difference is that B36.19M does not include all the heavier schedules (100, 120, 140, 160) available for carbon steel.

DN (Diamètre Nominal) is the metric designation equivalent to NPS (Nominal Pipe Size). Common equivalents: NPS 1/2 = DN 15, NPS 3/4 = DN 20, NPS 1 = DN 25, NPS 1-1/2 = DN 40, NPS 2 = DN 50, NPS 3 = DN 80, NPS 4 = DN 100, NPS 6 = DN 150, NPS 8 = DN 200, NPS 10 = DN 250, NPS 12 = DN 300. The DN number is approximately equal to the pipe’s inside diameter in millimeters for Schedule 40 sizes, but like NPS, it is a nominal designation — not an exact measurement.

Yes. Click the Print / PDF button above the table to open your browser’s print dialog, then select “Save as PDF” as the destination. The print stylesheet automatically hides the interactive controls and formats the table for paper. You can filter the table first (by pipe size or schedule) to print only the rows you need.