STANDARD · ASME-B16-5
ASME B16.5 Flange Dimensions
ASME B16.5-2025 · ASME B16.5
ASME B16.5 is the baseline American flange standard for pipe sizes NPS 1/2 to NPS 24 in pressure classes 150 through 2500. It defines outside diameter, flange thickness, raised-face diameter and height, bolt circle, bolt count, bolt hole diameter and hub geometry for weld neck, slip-on, blind, socket-weld, threaded and lap-joint flanges.
Because B16.5 is organised by nominal pipe size and class, a flange is only interchangeable with another B16.5 flange of the same size, class and facing. Class sets the wall thickness, bolt count and bolt size; the actual allowable pressure is read from the B16.5 pressure–temperature tables for the material group and design temperature. Above NPS 24, ASME B16.47 takes over — the two standards are not interchangeable. Coverage limits are part of the standard: Class 2500 runs only to NPS 12 and has no slip-on flanges, Class 1500 slip-on flanges stop at NPS 2-1/2, and Classes 900, 1500 and 2500 have no NPS 3-1/2.
DIMENSIONS
Dimension tables
One row per specification. Open a size for the drawing, pressure ratings and printable A4 sheet.
Weld Neck: Butt-welded to the pipe with a tapered hub; used for high pressure, high temperature and cyclic service. 136 specifications.
| Size | Rating | Outside Ø D | Thickness C | Raised face D2 | Bolt circle K | Bolting | Hub A | Length H | Weight | |
|---|---|---|---|---|---|---|---|---|---|---|
| 1/2″DN15 | 88.9 | 9.7 | 35.1 | 60.5 | 4 × Ø15.9 | 30.2 | 46 | 0.9 kg | Spec sheet | |
| 3/4″DN20 | 98.6 | 11.2 | 42.9 | 69.9 | 4 × Ø15.9 | 38.1 | 50.8 | 0.9 kg | Spec sheet | |
| 1″DN25 | 108 | 12.7 | 50.8 | 79.2 | 4 × Ø15.9 | 49.3 | 53.8 | 1.4 kg | Spec sheet | |
| 1¼″DN32 | 117.3 | 14.2 | 63.5 | 88.9 | 4 × Ø15.9 | 58.7 | 55.6 | 1.4 kg | Spec sheet | |
| 1½″DN40 | 127 | 15.7 | 73.2 | 98.6 | 4 × Ø15.9 | 65 | 60.5 | 1.8 kg | Spec sheet | |
| 2″DN50 | 152.4 | 17.5 | 91.9 | 120.7 | 4 × Ø19.1 | 77.7 | 62 | 2.7 kg | Spec sheet | |
| 2½″DN65 | 177.8 | 20.6 | 104.6 | 139.7 | 4 × Ø19.1 | 90.4 | 68.3 | 3.6 kg | Spec sheet | |
| 3″DN80 | 190.5 | 22.4 | 127 | 152.4 | 4 × Ø19.1 | 108 | 68.3 | 4.5 kg | Spec sheet | |
| 3½″DN90 | 215.9 | 22.4 | 139.7 | 177.8 | 8 × Ø19.1 | 122.2 | 69.9 | 5.4 kg | Spec sheet | |
| 4″DN100 | 228.6 | 22.4 | 157.2 | 190.5 | 8 × Ø19.1 | 134.9 | 74.7 | 6.8 kg | Spec sheet | |
| 5″DN125 | 254 | 22.4 | 185.7 | 215.9 | 8 × Ø22.2 | 163.6 | 87.4 | 8.6 kg | Spec sheet | |
| 6″DN150 | 279.4 | 23.9 | 215.9 | 241.3 | 8 × Ø22.2 | 192 | 87.4 | 10.9 kg | Spec sheet | |
| 8″DN200 | 342.9 | 26.9 | 269.7 | 298.5 | 8 × Ø22.2 | 246.1 | 100.1 | 17.7 kg | Spec sheet | |
| 10″DN250 | 406.4 | 28.4 | 323.9 | 362 | 12 × Ø25.4 | 304.8 | 100.1 | 23.6 kg | Spec sheet | |
| 12″DN300 | 482.6 | 30.2 | 381 | 431.8 | 12 × Ø25.4 | 365.3 | 112.8 | 36.3 kg | Spec sheet | |
| 14″DN350 | 533.4 | 33.3 | 412.8 | 476.3 | 12 × Ø28.6 | 400.1 | 125.5 | 49.9 kg | Spec sheet | |
| 16″DN400 | 596.9 | 35.1 | 469.9 | 539.8 | 16 × Ø28.6 | 457.2 | 125.5 | 63.5 kg | Spec sheet | |
| 18″DN450 | 635 | 38.1 | 533.4 | 577.9 | 16 × Ø31.8 | 505 | 138.2 | 68 kg | Spec sheet | |
| 20″DN500 | 698.5 | 41.1 | 584.2 | 635 | 20 × Ø31.8 | 558.8 | 142.7 | 81.6 kg | Spec sheet | |
| 22″DN550 | 749.3 | 44.5 | 641.4 | 692.2 | 20 × Ø28.6 | 609.6 | 147.8 | — | Spec sheet | |
| 24″DN600 | 812.8 | 46 | 692.2 | 749.3 | 20 × Ø34.9 | 663.4 | 150.9 | 118 kg | Spec sheet |
REFERENCE
Pressure ratings, materials and tolerances
Transcribed from ASME B16.5-2025 with table and page references.
ASME B16.5-2025 pressure ratings by material group
Tables 2-1.1 (SI units, bar) and 2-1.1C (U.S. Customary units, psig) of ASME B16.5-2025 give the maximum allo…
Open reference Material groupsASME B16.5-2025 material groups and bolting tables
Table 1.1-1 is the master material list of ASME B16.5-2025. For every accepted material it gives four things:…
Open reference TolerancesASME B16.5-2025 flange tolerances (Section 7)
Section 7 of ASME B16.5-2025 sets the manufacturing and inspection tolerances for flanges and flanged fitting…
Open reference MarkingASME B16.5-2025 marking requirements (Section 4)
Section 4 of ASME B16.5-2025 defines the identification markings that must be applied to flanges and flanged …
Open reference Edition changesASME B16.5-2025: what changed from the 2020 edition
ASME B16.5-2025 is the current edition of the American pipe-flange and flanged-fitting standard, covering NPS…
Open referenceHow to read the pressure class
ASME classes are not fixed pressures. For ASTM A105 (material group 1.1) the ASME B16.5-2025 ambient rating is 285 psi (19.6 bar) at Class 150, 740 psi (51.0 bar) at Class 300, 985 psi (68.0 bar) at Class 400, 1,480 psi (102.0 bar) at Class 600, 2,220 psi (153.1 bar) at Class 900, 3,705 psi (255.1 bar) at Class 1500 and 6,170 psi (425.1 bar) at Class 2500 at 38 °C (100 °F), derating as temperature rises. The 2025 edition revised the rating tables (record 23-2509); these are the 2025 values and the full temperature tables are on the ASME B16.5 pressure-ratings page.
Edition and verification
Dimension values on this page have been checked cell by cell against ASME B16.5-2025, using both the SI and U.S. Customary tables. The 2025 edition revised the bore (B) dimension figures and the minimum hub-height method, neither of which is a field published in these tables; outside diameter, thickness, hub, length, bolt circle and bolt-hole values match the 2025 edition. Raised-face height follows the 2025 rule: 1.5 mm for Classes 150 and 300, 6.4 mm for Classes 400 to 2500.
Data imported 2026-11-05 08:05.