Flange Dimensions Chart (ASME B16.5)
This flange dimensions chart gives the main dimensions of ASME B16.5 pipe flanges from ½" to 24" NPS in Class 150, 300 and 600: outside diameter, minimum flange thickness, bolt circle diameter, number of bolts and bolt hole diameter. These dimensions are common to weld neck, slip-on, socket weld, threaded, lap joint and blind flanges of the same size and class, so flanges of different types mate with each other.
How to use the chart
Find the nominal pipe size (NPS) and pressure class of the flange. The outside diameter, bolt circle and bolting must match the mating flange or valve. Minimum thickness is the flange ring thickness; for Class 150 and 300 it includes the 1.6 mm (1/16") raised face, and for Class 400 and above it excludes the 6.4 mm (¼") raised face. Hub dimensions, bores and lengths through the hub differ by flange type and are given in ASME B16.5. Larger sizes, from 26" to 60", are covered by ASME B16.47 Series A and B.
Class 150
| NPS | Outside diameter | Min. thickness | Bolt circle | No. of bolts | Bolt hole |
|---|---|---|---|---|---|
| ½ | 90 | 9.6 | 60.3 | 4 | 16 |
| ¾ | 100 | 11.2 | 69.9 | 4 | 16 |
| 1 | 110 | 12.7 | 79.4 | 4 | 16 |
| 1¼ | 115 | 14.3 | 88.9 | 4 | 16 |
| 1½ | 125 | 15.9 | 98.4 | 4 | 16 |
| 2 | 150 | 17.5 | 120.7 | 4 | 19 |
| 2½ | 180 | 20.7 | 139.7 | 4 | 19 |
| 3 | 190 | 22.3 | 152.4 | 4 | 19 |
| 4 | 230 | 22.3 | 190.5 | 8 | 19 |
| 5 | 255 | 22.3 | 215.9 | 8 | 22 |
| 6 | 280 | 23.9 | 241.3 | 8 | 22 |
| 8 | 345 | 27.0 | 298.5 | 8 | 22 |
| 10 | 405 | 28.6 | 362.0 | 12 | 25 |
| 12 | 485 | 30.2 | 431.8 | 12 | 25 |
| 14 | 535 | 33.4 | 476.3 | 12 | 29 |
| 16 | 595 | 35.0 | 539.8 | 16 | 29 |
| 18 | 635 | 38.1 | 577.9 | 16 | 32 |
| 20 | 700 | 41.3 | 635.0 | 20 | 32 |
| 24 | 815 | 46.1 | 749.3 | 20 | 35 |
Class 300
| NPS | Outside diameter | Min. thickness | Bolt circle | No. of bolts | Bolt hole |
|---|---|---|---|---|---|
| ½ | 95 | 12.7 | 66.7 | 4 | 16 |
| ¾ | 115 | 14.3 | 82.6 | 4 | 19 |
| 1 | 125 | 15.9 | 88.9 | 4 | 19 |
| 1¼ | 135 | 17.5 | 98.4 | 4 | 19 |
| 1½ | 155 | 19.1 | 114.3 | 4 | 22 |
| 2 | 165 | 20.7 | 127.0 | 8 | 19 |
| 2½ | 190 | 23.9 | 149.2 | 8 | 22 |
| 3 | 210 | 27.0 | 168.3 | 8 | 22 |
| 4 | 255 | 30.2 | 200.0 | 8 | 22 |
| 5 | 280 | 33.4 | 235.0 | 8 | 22 |
| 6 | 320 | 35.0 | 269.9 | 12 | 22 |
| 8 | 380 | 39.7 | 330.2 | 12 | 25 |
| 10 | 445 | 46.1 | 387.4 | 16 | 29 |
| 12 | 520 | 49.3 | 450.8 | 16 | 32 |
| 14 | 585 | 52.4 | 514.4 | 20 | 32 |
| 16 | 650 | 55.6 | 571.5 | 20 | 35 |
| 18 | 710 | 58.8 | 628.6 | 24 | 35 |
| 20 | 775 | 62.0 | 685.8 | 24 | 35 |
| 24 | 915 | 68.3 | 812.8 | 24 | 41 |
Class 600
| NPS | Outside diameter | Min. thickness | Bolt circle | No. of bolts | Bolt hole |
|---|---|---|---|---|---|
| ½ | 95 | 14.3 | 66.7 | 4 | 16 |
| ¾ | 115 | 15.9 | 82.6 | 4 | 19 |
| 1 | 125 | 17.5 | 88.9 | 4 | 19 |
| 1¼ | 135 | 20.7 | 98.4 | 4 | 19 |
| 1½ | 155 | 22.3 | 114.3 | 4 | 22 |
| 2 | 165 | 25.4 | 127.0 | 8 | 19 |
| 2½ | 190 | 28.6 | 149.2 | 8 | 22 |
| 3 | 210 | 31.8 | 168.3 | 8 | 22 |
| 4 | 275 | 38.1 | 215.9 | 8 | 25 |
| 5 | 330 | 44.5 | 266.7 | 8 | 29 |
| 6 | 355 | 47.7 | 292.1 | 12 | 29 |
| 8 | 420 | 55.6 | 349.2 | 12 | 32 |
| 10 | 510 | 63.5 | 431.8 | 16 | 35 |
| 12 | 560 | 66.7 | 489.0 | 20 | 35 |
| 14 | 605 | 69.9 | 527.0 | 20 | 38 |
| 16 | 685 | 76.2 | 603.2 | 20 | 41 |
| 18 | 745 | 82.6 | 654.0 | 20 | 44 |
| 20 | 815 | 88.9 | 723.9 | 24 | 44 |
| 24 | 940 | 101.6 | 838.2 | 24 | 51 |
Class 900, 1500 and 2500
Dimensions for Class 900, 1500 and 2500 flanges are given in ASME B16.5; send us the size and class and we will confirm dimensions and weights for your enquiry. In these classes, ring type joint (RTJ) facings are common, and the ring groove number for each size is listed in the standard.
Notes
Dimensions are from ASME B16.5 (2013 and later editions) and are given for guidance; always refer to the current edition and the project specification for design and purchasing. Bolt hole diameters are the metric equivalents of the standard inch holes. Our flanges in every material and type are on the flanges page, including weld neck flanges, stainless steel flanges, carbon steel flanges and ASTM A105 flanges. More charts are on the technical resources page.
Frequently Asked Questions
Under ASME B16.5, a 4" Class 150 flange has an outside diameter of 230 mm (9"), with eight bolts on a 190.5 mm bolt circle.
They share the outside diameter, thickness, bolt circle and bolting for the same size and class, so they mate with each other; hub dimensions differ.
ASME B16.47 Series A and B covers flanges from 26" to 60" NPS.
For Class 150 and 300 the B16.5 thickness includes the 1.6 mm raised face; for Class 400 and above it excludes the 6.4 mm raised face.
For sizes up to 3" they are the same; from 4" upwards Class 600 flanges are larger, with different bolt circles and bolts.