Pipe Standards

The Five Standards With Tables Here

8 standards documents are compiled into 5 pages, 9,892 wall-thickness rows in all. Each page carries its own table of outside diameters (OD) and wall thicknesses, and each row states how far it has been checked instead of implying that all of it is equally solid.

6,996 of 9,892 rows are verified: confirmed against the standard itself or against two genuinely independent publishers, and passing the standard’s own mass formula. A single-source row is arithmetically self-consistent but rests on one publisher. A computed row has verified dimensions and a published mass that failed the formula, so the computed value is shown and the published one is never quoted. How this data was verified, and what could not be sets out the method in full.

The Same Nominal Size Is Not the Same Diameter

DN 65, the metric name for 2½-inch pipe, is the sharpest case. 6 outside-diameter families are in use across the world, and between them they give 4 different answers spanning 3.3 mm for a size everyone calls by one name.

ASME is the outlier, not the world. Every other series lands within a few tenths of 76 mm; ASME B36.10M alone says 73.0 mm. A difference of 3.3 mm on the same nominal size is a weld-preparation problem rather than a tolerance question, and a fitting bored for one will not seat on the other.

DN 65 is the sharpest case but not the only one. Set every family against the American series across the range and the disagreements have a shape: they are largest at the small sizes, close to nil through the middle, and modest again at the top. Anything inside the shaded band on the figure below is within the ±1% the pipe is made to, which means the two are the same pipe for every practical purpose. Anything outside it is not.

Two consequences follow, and they pull in opposite directions. The first is reassuring: for most of the range, arguing about which standard a merchant quoted is wasted effort, because the difference is smaller than the manufacturing tolerance either way. The second is not: at the sizes where the series genuinely part company, the gap is several times the tolerance, and no amount of care in ordering will make one seat in the other. Knowing which case you are in is the entire practical value of this page.

The nominal number measures nothing in any of these systems. Why nominal pipe size is not the diameter explains where the numbers came from, and the NPS to DN conversion table matches the inch and metric designations size by size.

Why the Standards Disagree at All

The divergence is not drift. It is written into the definition. ISO 6708, the standard that defines DN, calls it an alphanumeric designation of size indirectly related to the physical size, in millimetres, of the bore or outside diameter of the end connections — bore or outside diameter — and a note leaves each downstream standard to declare its own relationship. Most of them did, and they declared different ones. There was never a moment at which these systems agreed and then came apart.

The second mechanism is inheritance, and DIN 2458 states it in its own footnote: below DN 150 the European series descends from the British gas-thread tradition, ISO R7, while from DN 150 upward it adopts the American ANSI B2.1 and API 5L diameters outright. That one sentence explains the shape of the entire comparison — thirteen of twenty-two sizes identical to ASME, near-perfect agreement on large pipe, and every disagreement but one at DN 125 or below.

Nor are the two systems disjoint. EN 10220 contains the American 73.0 mm and 141.3 mm, as Series 3: its lowest tier, the one described as special-application sizes for which very few standardised accessories exist. The American diameters are recognised in Europe and simply not preferred, while in the other direction EN does not list the American ⅛-inch to 1¼-inch diameters at all. The Russian series overlaps the same way — thirteen of its forty-six diameters appear in EN 10220’s own Series 2 and 3, a shared older European metric tradition that EN demoted rather than a rival invention.

A series in these documents is therefore a preference ranking, not a boundary. A diameter dismissed to the third tier in one country can be the default in another, which is why two standards can disagree about what a size is while both containing the number the other one uses.

Why These Tables Are Keyed on Outside Diameter

Two of these five publish no DN column at all. A GOST pipe is designated by outside diameter and wall thickness, and GB/T 17395 is a flat list of permitted outside diameters. The DN values circulated for both are trade convention rather than standards text, so printing them as “per GOST” would claim an authority the document does not carry.

ASME B36.10M is the exception. It prints the inch designation, the metric designation and a schedule number in the same table, which is why the ASME B36.10M dimensions and weights are the only figures here that can be listed by nominal size and schedule — and why that standard, and not one of the metric ones, is the table behind the full pipe size chart on the front of this site. Everything else is keyed on the diameter you can measure.

What Could Not Be Verified

329 rows across these five pages could not be confirmed. They are published carrying a visible “could not be verified” label rather than dropped, because a silent gap is indistinguishable from a confident answer, and they divide into two kinds with two different causes.

6 of them are walls at the three smallest ASME sizes that a widely-copied source publishes and the standard itself does not contain. The other 323 are single-digit typos in the GOST tables for which no upstream correction exists. Those cannot be closed by looking again: every accessible copy of those tables online descends from the same scan, so a second look returns the same typo and reads like confirmation. Errors found in published pipe data, and in ours lists them one by one, and every source used and how each was obtained says which standards are paywalled and what was used in their place.

Data revision: 2026-08-16. Wall tables compiled 2026-08-16.

Frequently Asked Questions

Which pipe standard applies in my country?

Five standards are published here, each with its own table: ASME B36.10M-2015 — United States, and the international default; EN 10220:2002 — Europe; JIS G3452 and G3454 — Japan; GOST 8732, 8734 and 10704 — Russia and the CIS; GB/T 17395-2008 — China. What changes between them is the outside diameter, and at some sizes it changes by more than three millimetres. A sixth series, the ISO 65 and BS 1387 threadable tube family, is in wide use and appears in the diameter comparison on this page, but its wall tables are not compiled here.

Is DN 65 pipe 73 mm or 76.1 mm across the outside?

Both, depending on which standard the pipe was made to. ASME B36.10M puts DN 65 at 73.0 mm. EN 10220 and the ISO 65 series put it at 76.1 mm, and JIS at 76.3 mm. ASME is the dissenter: every other series lands within a few tenths of 76 mm.

Do the standards share wall thicknesses as well as diameters?

No. Each publishes its own wall series against its own list of outside diameters, and the lists are not even the same length — the ASME table has 44 outside diameters, the GB/T table has 100. Where two standards do share a diameter, they rarely share the same set of walls.

Why do these tables have no DN column?

Because two of the standards do not publish one. GOST and GB/T designate a pipe by its outside diameter and wall thickness, full stop, and the DN numbers circulated for them are trade convention rather than standards text. Keying every table on the outside diameter is the only form that is true of all five.