For your review we present some information on a variety of flanges and related information.
Flange dimensions, Flange Bolt sizes, Number of flange bolts, Diameter of Flange bolts, Length of Flange bolts
Flange dimensions are determined by the pipe size and pressure class required for the application.
These dimensions have been standardized and published as ANSI, ASME, API or other standardization organization specifications.
ASME/ANSI B16.5 provides dimensions and tolerances for flanges in pipe sizes from 1/2″ through 24″ and in classes ranging 150 through 2500.
| Nominal Pipe Size NPS (inches) |
Class 150 | |||
| Diameter of Flange (inches) |
No. of Bolts |
Diameter of Bolts (inches) |
Bolt Circle (inches) |
|
| 1/4 | 3-3/8 | 4 | 1/2 | 2-1/4 |
| 1/2 | 3-1/2 | 4 | 1/2 | 2-3/8 |
| 3/4 | 3-7/8 | 4 | 1/2 | 2-3/4 |
| 1 | 4-1/4 | 4 | 1/2 | 3-1/8 |
| 1-1/4 | 4-5/8 | 4 | 1/2 | 3-1/2 |
| 1-1/2 | 5 | 4 | 1/2 | 3-7/8 |
| 2 | 6 | 4 | 5/8 | 4-3/4 |
| 2-1/2 | 7 | 4 | 5/8 | 5-1/2 |
| 3 | 7-1/2 | 4 | 5/8 | 6 |
| 3-1/2 | 8-1/2 | 8 | 5/8 | 7 |
| 4 | 9 | 8 | 5/8 | 7-1/2 |
| 5 | 10 | 8 | 3/4 | 8-1/2 |
| 6 | 11 | 8 | 3/4 | 9-1/2 |
| 8 | 13-1/2 | 8 | 3/4 | 11-3/4 |
| 10 | 16 | 12 | 7/8 | 14-1/4 |
| 12 | 19 | 12 | 7/8 | 17 |
| 14 | 21 | 12 | 1 | 18-3/4 |
| 16 | 23-1/2 | 16 | 1 | 21-1/4 |
| 18 | 25 | 16 | 1-1/8 | 22-3/4 |
| 20 | 27-1/2 | 20 | 1-1/8 | 25 |
| 24 | 32 | 20 | 1-1/4 | 29-1/2 |
| Nominal Pipe Size NPS (inches) |
Class 300 | |||
| Diameter of Flange (inches) |
No. of Bolts |
Diameter of Bolts (inches) |
Bolt Circle (inches) |
|
| 1/4 | 3-3/8 | 4 | 1/2 | 2-1/4 |
| 1/2 | 3-3/4 | 4 | 1/2 | 2-5/8 |
| 3/4 | 4-5/8 | 4 | 5/8 | 3-1/4 |
| 1 | 4-7/8 | 4 | 5/8 | 3-1/2 |
| 1-1/4 | 5-1/4 | 4 | 5/8 | 3-7/8 |
| 1-1/2 | 6-1/8 | 4 | 3/4 | 4-1/2 |
| 2 | 6-1/2 | 8 | 5/8 | 5 |
| 2-1/2 | 7-1/2 | 8 | 3/4 | 5-7/8 |
| 3 | 8-1/4 | 8 | 3/4 | 6-5/8 |
| 3-1/2 | 9 | 8 | 3/4 | 7-1/4 |
| 4 | 10 | 8 | 3/4 | 7-7/8 |
| 5 | 11 | 8 | 3/4 | 9-1/4 |
| 6 | 12-1/2 | 12 | 3/4 | 10-5/8 |
| 8 | 15 | 12 | 7/8 | 13 |
| 10 | 17-1/2 | 16 | 1 | 15-1/4 |
| 12 | 20-1/2 | 16 | 1-1/8 | 17-3/4 |
| 14 | 23 | 20 | 1-1/8 | 20-1/4 |
| 16 | 25-1/2 | 20 | 1-1/4 | 22-1/2 |
| 18 | 28 | 24 | 1-1/4 | 24-3/4 |
| 20 | 30-1/2 | 24 | 1-1/4 | 27 |
| 24 | 36 | 24 | 1-1/2 | 32 |
| Nominal Pipe Size NPS (inches) |
Class 400 | |||
| Diameter of Flange (inches) |
No. of Bolts |
Diameter of Bolts (inches) |
Bolt Circle (inches) |
|
| 1/4 | 3-3/8 | 4 | 1/2 | 2-1/4 |
| 1/2 | 3-3/4 | 4 | 1/2 | 2-5/8 |
| 3/4 | 4-5/8 | 4 | 5/8 | 3-1/4 |
| 1 | 4-7/8 | 4 | 5/8 | 3-1/2 |
| 1-1/4 | 5-1/4 | 4 | 5/8 | 3-7/8 |
| 1-1/2 | 6-1/8 | 4 | 3/4 | 4-1/2 |
| 2 | 6-1/2 | 8 | 5/8 | 5 |
| 2-1/2 | 7-1/2 | 8 | 3/4 | 5-7/8 |
| 3 | 8-1/4 | 8 | 3/4 | 6-5/8 |
| 3-1/2 | 9 | 8 | 7/8 | 7-1/4 |
| 4 | 10 | 8 | 7/8 | 7-7/8 |
| 5 | 11 | 8 | 7/8 | 9-1/4 |
| 6 | 12-1/2 | 12 | 7/8 | 10-5/8 |
| 8 | 15 | 12 | 1 | 13 |
| 10 | 17-1/2 | 16 | 1-1/8 | 15-1/4 |
| 12 | 20-1/2 | 16 | 1-1/4 | 17-3/4 |
| 14 | 23 | 20 | 1-1/4 | 20-1/4 |
| 16 | 25-1/2 | 20 | 1-3/8 | 22-1/2 |
| 18 | 28 | 24 | 1-3/8 | 24-3/4 |
| 20 | 30-1/2 | 24 | 1-1/2 | 27 |
| 24 | 36 | 24 | 1-3/4 | 32 |
| Nominal Pipe Size NPS (inches) |
Class 600 | |||
| Diameter of Flange (inches) |
No. of Bolts |
Diameter of Bolts (inches) |
Bolt Circle (inches) |
|
| 1/4 | 3-3/8 | 4 | 1/2 | 2-1/4 |
| 1/2 | 3-3/4 | 4 | 1/2 | 2-5/8 |
| 3/4 | 4-5/8 | 4 | 5/8 | 3-1/4 |
| 1 | 4-7/8 | 4 | 5/8 | 3-1/2 |
| 1-1/4 | 5-1/4 | 4 | 5/8 | 3-7/8 |
| 1-1/2 | 6-1/8 | 4 | 3/4 | 4-1/2 |
| 2 | 6-1/2 | 8 | 5/8 | 5 |
| 2-1/2 | 7-1/2 | 8 | 3/4 | 5-7/8 |
| 3 | 8-1/4 | 8 | 3/4 | 6-5/8 |
| 3-1/2 | 9 | 8 | 7/8 | 7-1/4 |
| 4 | 10-3/4 | 8 | 7/8 | 8-1/2 |
| 5 | 13 | 8 | 1 | 10-1/2 |
| 6 | 14 | 12 | 1 | 11-1/2 |
| 8 | 16-1/2 | 12 | 1-1/8 | 13-3/4 |
| 10 | 20 | 16 | 1-1/4 | 17 |
| 12 | 22 | 20 | 1-1/4 | 19-1/4 |
| 14 | 23-3/4 | 20 | 1-3/8 | 20-3/4 |
| 16 | 27 | 20 | 1-1/2 | 23-3/4 |
| 18 | 29-1/4 | 20 | 1-5/8 | 25-3/4 |
| 20 | 32 | 24 | 1-5/8 | 28-1/2 |
| 24 | 37 | 24 | 1-7/8 | 33 |
| Nominal Pipe Size NPS (inches) |
Class 900 | |||
| Diameter of Flange (inches) |
No. of Bolts |
Diameter of Bolts (inches) |
Bolt Circle (inches) |
|
| 1/2 | 4-3/4 | 4 | 3/4 | 3-1/4 |
| 3/4 | 5-1/8 | 4 | 3/4 | 3-1/2 |
| 1 | 5-7/8 | 4 | 7/8 | 4 |
| 1-1/4 | 6-1/4 | 4 | 7/8 | 4-3/8 |
| 1-1/2 | 7 | 4 | 1 | 4-7/8 |
| 2 | 8-1/2 | 8 | 7/8 | 6-1/2 |
| 2-1/2 | 9-5/8 | 8 | 1 | 7-1/2 |
| 3 | 9-1/2 | 8 | 7/8 | 7-1/2 |
| 4 | 11-1/2 | 8 | 1-1/8 | 9-1/4 |
| 5 | 13-3/4 | 8 | 1-1/4 | 11 |
| 6 | 15 | 12 | 1-1/8 | 12-1/2 |
| 8 | 18-1/2 | 12 | 1-3/8 | 15-1/2 |
| 10 | 21-1/2 | 16 | 1-3/8 | 18-1/2 |
| 12 | 24 | 20 | 1-3/8 | 21 |
| 14 | 25-1/4 | 20 | 1-1/2 | 22 |
| 16 | 27-3/4 | 20 | 1-5/8 | 24-1/2 |
| 18 | 31 | 20 | 1-7/8 | 27 |
| 20 | 33-3/4 | 20 | 2 | 29-1/2 |
| 24 | 41 | 20 | 2-1/2 | 35-1/2 |
| Nominal Pipe Size NPS (inches) |
Class 1500 | |||
| Diameter of Flange (inches) |
No. of Bolts |
Diameter of Bolts (inches) |
Bolt Circle (inches) |
|
| 1/2 | 4-3/4 | 4 | 3/4 | 3-1/4 |
| 3/4 | 5-1/8 | 4 | 3/4 | 3-1/2 |
| 1 | 5-7/8 | 4 | 7/8 | 4 |
| 1-1/4 | 6-1/4 | 4 | 7/8 | 4-3/8 |
| 1-1/2 | 7 | 4 | 1 | 4-7/8 |
| 2 | 8-1/2 | 8 | 7/8 | 6-1/2 |
| 2-1/2 | 9-5/8 | 8 | 1 | 7-1/2 |
| 3 | 10-1/2 | 8 | 1-1/8 | 8 |
| 4 | 12-1/4 | 8 | 1-1/4 | 9-1/2 |
| 5 | 14-3/4 | 8 | 1-1/2 | 11-1/2 |
| 6 | 15-1/2 | 12 | 1-3/8 | 12-1/2 |
| 8 | 19 | 12 | 1-5/8 | 15-1/2 |
| 10 | 23 | 12 | 1-7/8 | 19 |
| 12 | 26-1/2 | 16 | 2 | 22-1/2 |
| 14 | 29-1/2 | 16 | 2-1/4 | 25 |
| 16 | 32-1/2 | 16 | 2-1/2 | 27-3/4 |
| 18 | 36 | 16 | 2-3/4 | 30-1/2 |
| 20 | 38-3/4 | 16 | 3 | 32-3/4 |
| 24 | 46 | 16 | 3-1/2 | 39 |
| Nominal Pipe Size NPS (inches) |
Class 2500 | |||
| Diameter of Flange (inches) |
No. of Bolts |
Diameter of Bolts (inches) |
Bolt Circle (inches) |
|
| 1/2 | 5-1/4 | 4 | 3/4 | 3-1/2 |
| 3/4 | 5-1/2 | 4 | 3/4 | 3-3/4 |
| 1 | 6-1/4 | 4 | 7/8 | 4-1/4 |
| 1-1/4 | 7-1/4 | 4 | 1 | 5-1/8 |
| 1-1/2 | 8 | 4 | 1-1/8 | 5-3/4 |
| 2 | 9-1/4 | 8 | 1 | 6-3/4 |
| 2-1/2 | 10-1/2 | 8 | 1-1/8 | 7-3/4 |
| 3 | 12 | 8 | 1-1/4 | 9 |
| 4 | 14 | 8 | 1-1/2 | 10-3/4 |
| 5 | 16-1/2 | 8 | 1-3/4 | 12-3/4 |
| 6 | 19 | 8 | 2 | 14-1/2 |
| 8 | 21-3/4 | 12 | 2 | 17-1/4 |
| 10 | 26-1/2 | 12 | 2-1/2 | 21-1/4 |
| 12 | 30 | 12 | 2-3/4 | 24-3/8 |
