Huiya · Technical Reference

DN to Inch Pipe Size Chart — with mm OD across Metric, ANSI Sch 80 & JIS

Convert DN to inch and back, and read the real outside diameter (OD) in mm for the same nominal size under three plastic-pipe standards: metric/DIN, ANSI Schedule 80, and JIS. Type any size below, or read the full pipe size chart (inch and mm) further down.

Pipe size converter

Enter an inch size, DN, metric dn or an OD in mm — e.g. 2″, DN50, dn63 or 60.

Metric / DIN

mm OD (dn)

ANSI Sch 80

mm OD

JIS

mm OD

Plastic pipe size chart — inch, DN and OD (mm)

Nominal sizeinch / DN	Metric / DINOD mm (dn)	ANSI Sch 80OD mm	JISOD mm
3/8″DN10	16	17.14	18
1/2″DN15	20	21.34	22
3/4″DN20	25	26.67	26
1″DN25	32	33.4	32
1-1/4″DN32	40	42.16	38
1-1/2″DN40	50	48.26	48
2″DN50	63	60.33	60
2-1/2″DN65	75	73.03	76
3″DN80	90	88.9	89
4″DN100	110	114.3	114
5″DN125	140	141.3	140
6″DN150	160	168.28	165
8″DN200	225	219.08	216
10″DN250	280	273.05	267
12″DN300	315	323.85	318

Nominal outside diameter shown in mm; tolerances vary by standard, schedule and pressure class. Metric values follow the DIN/ISO dn series (also used in GB). ANSI Sch 40 and Sch 80 share the same OD. Always confirm dimensions against the governing standard for pressure-critical work.

How to read this chart (and why the standards don’t interchange)

A “2-inch” pipe, DN50 and dn63 all describe the same nominal size — but the actual outside diameter is not the same in every system. Metric/DIN pipe is named by its OD, so a dn63 pipe really is 63 mm across. ANSI (inch-based) pipe of the same nominal 2″ measures about 60.3 mm, and JIS lands near 60 mm. The nominal name matches; the millimetres do not.

That gap is why pipe and fittings from different standards do not bolt or solvent-weld together reliably: the diameters, and on flanged ends the bolt circles, simply differ. The practical rule is to keep pipe, fittings and valves on a single standard end to end, and to use this chart only to identify the nearest equivalent — not as a licence to mix systems.

Which valve fits your size?

Thermoplastic valves are ordered by DN, so once you have the size you can go straight to the pattern. Not every valve type covers every size — ball valves stop roughly where butterfly valves take over, and diaphragm valves sit in between.

Valveconnection	Size rangeDN	Inchequivalent
True union ball valveDouble union	DN15 – DN100	1/2″ – 4″
Flanged ball valveBolted flange	DN25 – DN200	1″ – 8″
Butterfly valveWafer / lug	DN25 – DN500	1″ – 20″
Diaphragm valveUnion	DN15 – DN50	1/2″ – 2″
Diaphragm valveBolted flange	DN25 – DN200	1″ – 8″

Rule of thumb: below DN80, a ball valve is the cheapest reliable on/off shut-off; from DN80 upwards a butterfly valve is lighter, cheaper and easier to actuate; and wherever the medium carries solids or crystallises out, use a diaphragm valve at any size.

All patterns are rated PN10, seal on a PTFE seat with EPDM or FKM O-rings, and are built in UPVC, CPVC, PPH or PVDF, manual or pneumatically actuated.

Ordering a valve: quote the standard, not just the size

One more thing to quote alongside the size: the flange standard. ANSI Class 150, DIN PN10/PN16 and JIS 10K are not interchangeable, and at DN80 they do not even share the same number of bolts. Full bolt counts and bolt-circle diameters for all three standards are in our ANSI, DIN and JIS flange drilling table.

Standardcommon in	Flange drillingplastic valves	Sized asnominal basis
DIN / ENEurope, China, most of Asia	PN10 / PN16	DN, metric OD
ANSI / ASTMNorth America	Class 150	NPS, Schedule 80
JISJapan, parts of Southeast Asia	10K	JIS metric

Give us the standard with the size. Huiya builds to ISO 16135 and drills every valve to DIN, ANSI or JIS, so a valve ordered against the right standard bolts straight into the existing line. For UPVC and CPVC, valves conform to ASTM F1970 and socket ends follow ASTM D2467 Schedule 80.

Size is only half the specification — what survives the medium is decided by the body material: UPVC for ambient water and mild chemicals to ~55 °C, CPVC for hot and acidic duty to ~90 °C, PPH for strong caustic and alkalis, and PVDF for concentrated acids, halogens and high purity to ~120 °C. Weigh all four in our plastic valve material selection guide, or look your exact medium up in the chemical resistance checker.

Pipe size FAQ

Is DN the same as inch?

No. DN (diamètre nominal) is a metric label and inch (NPS) is the imperial label for the same nominal size — DN50 corresponds to 2″, DN100 to 4″, and so on. They are matching names, not equal measurements: the true OD in mm still depends on the standard, as the chart above shows.

What is DN50 in inches?

DN50 is the nominal equivalent of 2 inch. The OD is about 60.3 mm under ANSI, 60 mm under JIS, and 63 mm for metric/DIN dn63 pipe.

Is dn63 the same as 2 inch pipe?

By nominal size, yes — metric dn63 = DN50 = 2″. By outside diameter, not exactly: dn63 is 63 mm, while a 2″ ANSI pipe is ~60.3 mm. So a dn63 pipe will not fit a 2″ imperial fitting.

Does metric pipe fit ANSI or JIS fittings?

Generally no. The outside diameters differ by a few millimetres, and flanged connections have different bolt circles, so different standards are not interchangeable without an adapter or a transition fitting. Match everything to one standard.

What is the OD of 2 inch PVC pipe?

About 60.3 mm for ANSI Schedule 40/80 (they share the same OD). For metric/DIN it is 63 mm (dn63) and for JIS roughly 60 mm.

Will a DN50 valve fit my 2 inch ANSI line?

Only if it is drilled to the right standard. DN50 and 2″ are the same nominal size, but a DN50 valve drilled to DIN PN10 has a different bolt circle from an ANSI Class 150 flange — the bolts will not line up. Order the valve against the standard the line was built to, not just the size.

What sizes do plastic valves come in?

Ball valves run DN15–DN100 in the true union pattern and DN15–DN200 flanged; diaphragm valves DN15–DN200; butterfly valves DN25–DN500. As a rule, use a ball valve below DN80, a butterfly valve above it, and a diaphragm valve wherever the medium carries solids or crystallises out.

Need valves in a specific standard?

We manufacture UPVC, CPVC, PPH and PVDF valves — ball, butterfly and diaphragm, manual and pneumatic — drilled to ANSI Class 150, DIN PN10/16 or JIS 10K. Send your size, standard, material and media and our engineers will spec the exact match.

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