Dimension table · Flanges
ASME B16.5 flange dimensions: Class 150 to Class 2500
Bolt circle W, outside diameter O, raised-face diameter R and the number and diameter of holes Z × I (catalogue letters of the ASME world), plus pipe outside diameter and stud size – in separate tables per pressure class from Class 150 to Class 2500, nominal sizes in inches from 1/2" to 24". These flanges are still commercially known as “ANSI flanges” or “150/300/600 lbs” – but the class number is not a pressure rating in psi or pounds. Unlike DIN EN 1092-1, ASME flanges are not part of the scope of the European standard – always check which standard is required on international projects.
Hole diameter I ≠ bolt diameter: I is the bolt hole in the flange plate – the matching bolt is always thinner (clearance for assembly and alignment). Example: 19.1 mm hole → 3/4″ bolt, i.e. M16/UNC 3/4. The bolt size follows from the standard, not from the hole dimension.
Class 150 – connection dimensions (1/2"–24")
| NPS | Pipe OD (mm) 1 | Z × ØI – holes (mm) | Stud – bolts 2 | ØR – Raised Face (mm) | ØW – bolt circle (mm) | ØO – outside (mm) | Availability |
|---|---|---|---|---|---|---|---|
| 1/2" | 21.3 | 4 × 15.7 | 1/2" | 35.1 | 60.5 | 88.9 | available |
| 3/4" | 26.7 | 4 × 15.7 | 1/2" | 42.9 | 69.9 | 98.6 | available |
| 1" | 33.4 | 4 × 15.7 | 1/2" | 50.8 | 79.2 | 108 | available |
| 1 1/4" | 42.2 | 4 × 15.7 | 1/2" | 63.5 | 88.9 | 117.3 | available |
| 1 1/2" | 48.3 | 4 × 15.7 | 1/2" | 73.2 | 98.6 | 127 | available |
| 2" | 60.3 | 4 × 19.1 | 5/8" | 91.9 | 120.7 | 152.4 | available |
| 2 1/2" | 73.0 | 4 × 19.1 | 5/8" | 104.6 | 139.7 | 177.8 | available |
| 3" | 88.9 | 4 × 19.1 | 5/8" | 127 | 152.4 | 190.5 | available |
| 3 1/2" | 101.6 | 8 × 19.1 | 5/8" | 139.7 | 177.8 | 215.9 | available |
| 4" | 114.3 | 8 × 19.1 | 5/8" | 157.2 | 190.5 | 228.6 | available |
| 5" | 141.3 | 8 × 22.4 | 3/4" | 185.7 | 215.9 | 254 | available |
| 6" | 168.3 | 8 × 22.4 | 3/4" | 215.9 | 241.3 | 279.4 | available |
| 8" | 219.1 | 8 × 22.4 | 3/4" | 269.7 | 298.5 | 342.9 | available |
| 10" | 273.1 | 12 × 25.4 | 7/8" | 323.9 | 362 | 406.4 | available |
| 12" | 323.9 | 12 × 25.4 | 7/8" | 381 | 431.8 | 482.6 | available |
| 14" | 355.6 | 12 × 28.4 | 1" | 412.8 | 476.3 | 533.4 | available |
| 16" | 406.4 | 16 × 28.4 | 1" | 469.9 | 539.8 | 596.9 | available |
| 18" | 457.2 | 16 × 31.8 | 1 1/8" | 533.4 | 577.9 | 635 | available |
| 20" | 508.0 | 20 × 31.8 | 1 1/8" | 584.2 | 635 | 698.5 | available |
| 22" 3 | 558.8 | 20 × 35.1 | 1 1/4" | – | 692.1 | 749.3 | on request |
| 24" | 609.6 | 20 × 35.1 | 1 1/4" | 692.2 | 749.3 | 812.8 | available |
Class 300 – connection dimensions (1/2"–24")
| NPS | Pipe OD (mm) 1 | Z × ØI – holes (mm) | Stud – bolts 2 | ØR – Raised Face (mm) | ØW – bolt circle (mm) | ØO – outside (mm) | Availability |
|---|---|---|---|---|---|---|---|
| 1/2" | 21.3 | 4 × 15.7 | 1/2" | 35 | 66.5 | 95.2 | available |
| 3/4" | 26.7 | 4 × 19 | 5/8" | 42.9 | 82.5 | 117.3 | available |
| 1" | 33.4 | 4 × 19 | 5/8" | 50.8 | 88.9 | 123.9 | available |
| 1 1/4" | 42.2 | 4 × 19 | 5/8" | 63.5 | 98.5 | 133.3 | available |
| 1 1/2" | 48.3 | 4 × 22.3 | 3/4" | 73.1 | 114.3 | 155.4 | available |
| 2" | 60.3 | 8 × 19 | 5/8" | 91.9 | 127 | 165.1 | available |
| 2 1/2" | 73.0 | 8 × 22.3 | 3/4" | 104.6 | 149.3 | 190.5 | available |
| 3" | 88.9 | 8 × 22.3 | 3/4" | 127 | 168.1 | 209.5 | available |
| 3 1/2" | 101.6 | 8 × 22.3 | 3/4" | 139.7 | 184.1 | 228.6 | available |
| 4" | 114.3 | 8 × 22.3 | 3/4" | 157.2 | 200.1 | 254 | available |
| 5" | 141.3 | 8 × 22.3 | 3/4" | 185.6 | 234.9 | 279.4 | available |
| 6" | 168.3 | 12 × 22.3 | 3/4" | 215.9 | 269.7 | 317.5 | available |
| 8" | 219.1 | 12 × 25.4 | 7/8" | 269.7 | 330.2 | 381 | available |
| 10" | 273.1 | 16 × 28.4 | 1" | 323.8 | 387.3 | 444.5 | available |
| 12" | 323.9 | 16 × 31.7 | 1 1/8" | 381 | 450.8 | 520.7 | available |
| 14" | 355.6 | 20 × 31.7 | 1 1/8" | 412.7 | 514.3 | 584.2 | available |
| 16" | 406.4 | 20 × 35 | 1 1/4" | 469.9 | 571.5 | 647.7 | available |
| 18" | 457.2 | 24 × 35 | 1 1/4" | 533.4 | 628.6 | 711.2 | available |
| 20" | 508.0 | 24 × 35 | 1 1/4" | 584.2 | 685.8 | 774.7 | available |
| 22" 3 | 558.8 | 24 × 41.4 | 1 1/2" | – | 742.9 | 838.2 | on request |
| 24" | 609.6 | 24 × 41.1 | 1 1/2" | 692.1 | 812.8 | 914.4 | available |
Class 600 – connection dimensions (1/2"–24")
| NPS | Pipe OD (mm) 1 | Z × ØI – holes (mm) | Stud – bolts 2 | ØR – Raised Face (mm) | ØW – bolt circle (mm) | ØO – outside (mm) | Availability |
|---|---|---|---|---|---|---|---|
| 1/2" | 21.3 | 4 × 15.7 | 1/2" | 35.1 | 66.5 | 95.3 | available |
| 3/4" | 26.7 | 4 × 19.1 | 5/8" | 42.9 | 82.6 | 117.3 | available |
| 1" | 33.4 | 4 × 19.1 | 5/8" | 50.8 | 88.9 | 124 | available |
| 1 1/4" | 42.2 | 4 × 19.1 | 5/8" | 63.5 | 98.6 | 133.4 | available |
| 1 1/2" | 48.3 | 4 × 22.4 | 3/4" | 73.2 | 114.3 | 155.4 | available |
| 2" | 60.3 | 8 × 19.1 | 5/8" | 91.9 | 127 | 165.1 | available |
| 2 1/2" | 73.0 | 8 × 22.4 | 3/4" | 104.6 | 149.4 | 190.5 | available |
| 3" | 88.9 | 8 × 22.4 | 3/4" | 127 | 168.1 | 209.6 | available |
| 3 1/2" | 101.6 | 8 × 25.4 | 7/8" | 139.7 | 184.2 | 228.6 | available |
| 4" | 114.3 | 8 × 25.4 | 7/8" | 157.2 | 215.9 | 273.1 | available |
| 5" | 141.3 | 8 × 28.4 | 1" | 185.7 | 266.7 | 330.2 | available |
| 6" | 168.3 | 12 × 28.4 | 1" | 215.9 | 292.1 | 355.6 | available |
| 8" | 219.1 | 12 × 31.8 | 1 1/8" | 269.7 | 349.3 | 419.1 | available |
| 10" | 273.1 | 16 × 35.1 | 1 1/4" | 323.9 | 431.8 | 508 | available |
| 12" | 323.9 | 20 × 35.1 | 1 1/4" | 381 | 489 | 558.8 | available |
| 14" | 355.6 | 20 × 38.1 | 1 3/8" | 412.8 | 527 | 603.3 | available |
| 16" | 406.4 | 20 × 41.1 | 1 1/2" | 469.9 | 603.3 | 685.8 | available |
| 18" | 457.2 | 20 × 44.5 | 1 5/8" | 533.4 | 654.1 | 743 | available |
| 20" | 508.0 | 24 × 44.5 | 1 5/8" | 584.2 | 723.9 | 812.8 | available |
| 22" 3 | 558.8 | 24 × 44.4 | 1 5/8" | – | 778 | 869.9 | on request |
| 24" | 609.6 | 24 × 50.8 | 1 7/8" | 692.2 | 838.2 | 939.8 | available |
Class 900 – connection dimensions (1/2"–24")
| NPS | Pipe OD (mm) 1 | Z × ØI – holes (mm) | Stud – bolts 2 | ØR – Raised Face (mm) | ØW – bolt circle (mm) | ØO – outside (mm) | Availability |
|---|---|---|---|---|---|---|---|
| 1/2" 4 | 21.3 | 4 × 22.4 | 3/4" | 35.1 | 82.5 | 120.6 | available |
| 3/4" 4 | 26.7 | 4 × 22.4 | 3/4" | 42.9 | 88.9 | 130 | available |
| 1" 4 | 33.4 | 4 × 25.4 | 7/8" | 50.8 | 101.6 | 149.4 | available |
| 1 1/4" 4 | 42.2 | 4 × 25.4 | 7/8" | 63.5 | 111.3 | 158.8 | available |
| 1 1/2" 4 | 48.3 | 4 × 28.4 | 1" | 73.2 | 124 | 177.8 | available |
| 2" 4 | 60.3 | 8 × 25.4 | 7/8" | 91.9 | 165.1 | 215.9 | available |
| 2 1/2" 4 | 73.0 | 8 × 28.4 | 1" | 104.6 | 190.5 | 244.3 | available |
| 3" | 88.9 | 8 × 25.4 | 7/8" | 127 | 190.5 | 241.3 | available |
| 4" | 114.3 | 8 × 31.8 | 1 1/8" | 157.2 | 234.9 | 292.1 | available |
| 5" | 141.3 | 8 × 35.1 | 1 1/4" | 185.7 | 279.4 | 349.2 | available |
| 6" | 168.3 | 12 × 31.8 | 1 1/8" | 215.9 | 317.5 | 381 | available |
| 8" | 219.1 | 12 × 38.1 | 1 3/8" | 269.7 | 393.7 | 469.9 | available |
| 10" | 273.1 | 16 × 38.1 | 1 3/8" | 323.9 | 469.9 | 546.1 | available |
| 12" | 323.9 | 20 × 38.1 | 1 3/8" | 381 | 533.4 | 609.6 | available |
| 14" | 355.6 | 20 × 41.4 | 1 1/2" | 412.8 | 558.8 | 641.3 | available |
| 16" | 406.4 | 20 × 44.4 | 1 5/8" | 469.9 | 615.9 | 704.8 | available |
| 18" | 457.2 | 20 × 50.8 | 1 7/8" | 533.4 | 685.8 | 787.4 | available |
| 20" | 508.0 | 20 × 54.1 | 2" | 584.2 | 749.3 | 857.2 | available |
| 24" | 609.6 | 20 × 66.8 | 2 1/2" | 692.2 | 901.7 | 1041.4 | available |
Class 1500 – connection dimensions (1/2"–24")
| NPS | Pipe OD (mm) 1 | Z × ØI – holes (mm) | Stud – bolts 2 | ØR – Raised Face (mm) | ØW – bolt circle (mm) | ØO – outside (mm) | Availability |
|---|---|---|---|---|---|---|---|
| 1/2" | 21.3 | 4 × 22.4 | 3/4" | 35.1 | 82.5 | 120.6 | available |
| 3/4" | 26.7 | 4 × 22.4 | 3/4" | 42.9 | 88.9 | 130 | available |
| 1" | 33.4 | 4 × 25.4 | 7/8" | 50.8 | 101.6 | 149.4 | available |
| 1 1/4" | 42.2 | 4 × 25.4 | 7/8" | 63.5 | 111.3 | 158.8 | available |
| 1 1/2" | 48.3 | 4 × 28.4 | 1" | 73.2 | 124 | 177.8 | available |
| 2" | 60.3 | 8 × 25.4 | 7/8" | 91.9 | 165.1 | 215.9 | available |
| 2 1/2" | 73.0 | 8 × 28.4 | 1" | 104.6 | 190.5 | 244.3 | available |
| 3" | 88.9 | 8 × 31.8 | 1 1/8" | 127 | 203.2 | 266.7 | available |
| 4" | 114.3 | 8 × 35.1 | 1 1/4" | 157.2 | 241.3 | 311.1 | available |
| 5" | 141.3 | 8 × 41.4 | 1 1/2" | 185.7 | 292.1 | 374.6 | available |
| 6" | 168.3 | 12 × 38.1 | 1 3/8" | 215.9 | 317.5 | 393.7 | available |
| 8" | 219.1 | 12 × 44.4 | 1 5/8" | 269.7 | 393.7 | 482.6 | available |
| 10" | 273.1 | 12 × 50.8 | 1 7/8" | 323.9 | 482.6 | 584.2 | available |
| 12" | 323.9 | 16 × 53.8 | 2" | 381 | 571.5 | 673.1 | available |
| 14" | 355.6 | 16 × 60.5 | 2 1/4" | 412.8 | 635 | 749.3 | available |
| 16" | 406.4 | 16 × 66.8 | 2 1/2" | 469.9 | 704.8 | 825.5 | available |
| 18" | 457.2 | 16 × 73.2 | 2 3/4" | 533.4 | 774.7 | 914.4 | available |
| 20" | 508.0 | 16 × 79.2 | 3" | 584.2 | 831.8 | 984.2 | available |
| 24" | 609.6 | 16 × 92.2 | 3 1/2" | 692.2 | 990.6 | 1168.4 | available |
Class 2500 – connection dimensions (1/2"–12")
| NPS | Pipe OD (mm) 1 | Z × ØI – holes (mm) | Stud – bolts 2 | ØR – Raised Face (mm) | ØW – bolt circle (mm) | ØO – outside (mm) | Availability |
|---|---|---|---|---|---|---|---|
| 1/2" | 21.3 | 4 × 22.4 | 3/4" | 35.1 | 88.9 | 133.3 | available |
| 3/4" | 26.7 | 4 × 22.4 | 3/4" | 42.9 | 95.2 | 139.7 | available |
| 1" | 33.4 | 4 × 25.4 | 7/8" | 50.8 | 107.9 | 158.8 | available |
| 1 1/4" | 42.2 | 4 × 28.4 | 1" | 63.5 | 130.3 | 184.1 | available |
| 1 1/2" | 48.3 | 4 × 31.8 | 1 1/8" | 73.2 | 146 | 203.2 | available |
| 2" | 60.3 | 8 × 28.4 | 1" | 91.9 | 171.4 | 234.9 | available |
| 2 1/2" | 73.0 | 8 × 31.8 | 1 1/8" | 104.6 | 196.8 | 266.7 | available |
| 3" | 88.9 | 8 × 35.1 | 1 1/4" | 127 | 228.6 | 304.8 | available |
| 4" | 114.3 | 8 × 41.4 | 1 1/2" | 157.2 | 273.1 | 355.6 | available |
| 5" | 141.3 | 8 × 47.8 | 1 3/4" | 185.7 | 323.8 | 419.1 | available |
| 6" | 168.3 | 8 × 53.8 | 2" | 215.9 | 368.3 | 482.6 | available |
| 8" | 219.1 | 12 × 53.8 | 2" | 269.7 | 438.1 | 552.4 | available |
| 10" | 273.1 | 12 × 66.8 | 2 1/2" | 323.9 | 539.8 | 673.1 | available |
| 12" | 323.9 | 12 × 73.2 | 2 3/4" | 381 | 619.3 | 762 | available |
1 Pipe OD = outside diameter of the matching pipe to ASME B36.10M. The flange bore lies somewhat above this (clearance), depending on type, or follows the pipe inside diameter for the welding neck flange – see the note box above.
2 Stud = stud bolt diameter in inches (UNC thread). To ASME B16.5 the hole diameter ØI is always 1/8″ larger than the bolt.
3 22″ (DN 550) is not standardised in ASME B16.5, but is a common manufacturer standard in the trade (cf. MSS SP-44); raised-face diameter per manufacturer data – confirm the bolt-hole pattern and sealing face explicitly when ordering.
4 In Class 900, nominal sizes 1/2″ to 2 1/2″ are executed identically to Class 1500 to ASME B16.5.
Need larger diameters? Above 24″, sizing continues with ASME B16.47 Series A / Series B (NPS 26 – 60). The two series are geometrically different and must not be confused – contact us directly for these sizes.
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Send us your inquiryTechnical basis: ASME B16.5. All information without guarantee – the current standard texts and the manufacturers’ technical data sheets always prevail. Values selected according to our delivery and stock programme; compiled from our own ERP data and long-standing trading practice, cross-checked against publicly available manufacturer information. These tables do not replace the standard text – the current edition of the standard always governs. Editorially reviewed: July 2026. Standards and manufacturer status considered: July 2026.