Pipe sizes from 1/8" to 24" with OD, wall thickness and ID for schedule 40 and 80.
A pipe size reference covers Nominal Pipe Size (NPS), Diameter Nominal (DN), Schedule numbers, outer diameter, wall thickness, and weight per metre for standard steel pipes per ASME B36.10 / ASME B36.19. Pipe sizing for fluid systems is governed by required flow rate, pressure drop, and material velocity limits.
NPS is American (NPS 1, 2, 4, 6 — "inches"); DN is metric (DN 25, 50, 100, 150). They are interchangeable nominal designations: NPS 4 ≡ DN 100. Critically, the nominal size is NOT the actual OD or ID — NPS 2 pipe has an OD of 60.3 mm, not 50.8 mm.
ID = OD - 2 \times t
Inputs: NPS 4 (DN 100) pipe in Schedule 40
Both refer to wall thickness at the same nominal pipe size. Sch 80 has roughly 50% thicker walls than Sch 40, giving higher pressure rating and longer service life under corrosive conditions. For NPS 4: Sch 40 = 6.02 mm wall, Sch 80 = 8.56 mm wall. Use Sch 80 for chemical processing, steam, and elevated temperature service.
Use whichever your project drawings and specs use — don't mix. American projects, oil & gas, ASME B31 piping codes use NPS. European, ISO and Indian projects typically use DN. The two are nominally equivalent (NPS 4 ≡ DN 100) and pipe is sold interchangeably — what matters is the schedule (wall thickness) for both pressure and connection compatibility.
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