About

Why another pipe dimension table

Because the tables that exist answer a different question. They give a chart; they rarely say which measurement decides a fit, whether a wall is nominal or a minimum, or what a size name is actually worth in millimetres.

The confusion is measurable

“1/2 inch pipe” is 0.840 in / 21.336 mm outside if it is steel or PVC, and 0.625 in / 15.875 mm if it is PEX tubing. At NPS 12, the wall called STD is 0.375 in while Sch 40 is 0.406 in — so the habit of writing “STD = Sch 40” breaks at that size even where it holds elsewhere. Two names can describe one wall, and one name can describe two walls — in the same set of tables.

Every page here starts from the number you can measure — the outer diameter — and works outwards: measure to standard, two values to the third, name to name.

What is covered

• ASME B36.10M (welded and seamless steel pipe) — 17 sizes, 128 published values, 3 designation(s) held back
• ASTM D2241 (PVC pressure pipe) — 9 sizes, 18 published values
• ASTM F876/F877 (CTS) (PEX tubing (CTS)) — 9 sizes, 3 published values, 1 designation(s) held back
• ASME B36.19M (stainless steel pipe) — 17 sizes, 64 published values, 2 designation(s) held back

Not covered yet: copper tube (ASTM B88), CPVC, metric tube (EN 10220), and five PEX sizes whose wall we could not double-source. The reasons are on the sources page.

Three promises

1. Every published wall value names two independent sources, on the page.
2. Anything that fails the rule is said to be missing rather than estimated — including edition years we did not verify.
3. Derived numbers say what they came from. Bore is OD − 2 × wall; millimetres are inches × 25.4; mass assumes a density and says which one.

How it is built

CSV files with one row per size × designation go through a QA gate that enforces the two-source rule, the geometry check and an honest revision field. The gate emits JSON with a version digest; a static site (Astro) renders every number into the HTML, so pages work without JavaScript and a crawler sees the answer. The calculation engine is a framework-free TypeScript package shared by the tools, and the whole thing is checked by one script before a release goes live.

Data version 48d86b977106 · sources checked 2026-09-25 ·accuracy policy · sources.