ANSI Flange PCDs and Dimensions
This page on ANSI Flange PCDs and Dimensions is an excerpt from the original
ANSI / ASME B16.5 Flange Dimensions webpage published on the
Control And Instrumentation.comwebsite, and is reproduced here with their permission.
Flange dimensions are determined by pipe size and pressure class required for the application. These dimensions have been standardised and published by bodies such as The American National Standards Institute (ANSI).
ANSI B16.5. Flange PCD Dimensions
Dimensions for pitch circle diameter (PCD) of flange bolts, and the bolt sizes for the most common pipe sizes and flange ratings are shown in the tables below.
Note - All bolt holes are 1/8" larger than the diameter of the bolts.
See our page on
Stud and Nut Sizes to determine the correct nut size.
| ANSI 150# Flange PCD |
| Pipe NB | Bolt PCD | No. of Bolts | Bolt Size | Flange OD |
| 1/2" | 2 3/8" | 4 | 1/2" | 3 1/2" |
| 1" | 3 1/8" | 4 | 1/2" | 4 1/4" |
| 2" | 4 3/4" | 4 | 5/8" | 6" |
| 4" | 7 1/2" | 8 | 5/8" | 9" |
| 6" | 9 1/2" | 8 | 3/4" | 11" |
| 8" | 11 3/4" | 8 | 3/4" | 13 1/2" |
| 10" | 14 1/4" | 12 | 7/8" | 16" |
| 12" | 17 " | 12 | 7/8" | 19" |
| 14" | 18 3/4" | 12 | 1" | 21" |
| ANSI 300# Flange PCD |
| Pipe NB | Bolt PCD | No. of Bolts | Bolt Size | Flange OD |
| 1/2" | 2 5/8" | 4 | 1/2" | 3 3/4" |
| 1" | 3 1/2" | 4 | 5/8" | 4 7/8" |
| 2" | 5" | 8 | 5/8" | 6 1/2" |
| 4" | 7 7/8" | 8 | 3/4" | 10" |
| 6" | 10 5/8" | 12 | 3/4" | 12 1/2" |
| 8" | 13" | 12 | 7/8" | 15" |
| 10" | 15 1/4" | 16 | 1" | 17 1/2" |
| 12" | 17 3/4" | 16 | 1 1/8" | 20 1/2" |
| 14" | 20 1/4" | 20 | 1 1/8" | 23" |
| ANSI 600# |
| Pipe NB | Bolt PCD | No. of Bolts | Bolt Size | Flange OD |
| 1/2" | 2 5/8" | 4 | 1/2" | 3 3/4" |
| 1" | 3 1/2" | 4 | 5/8" | 4 7/8" |
| 2" | 5" | 8 | 5/8" | 6 1/2" |
| 4" | 8 1/2" | 8 | 7/8" | 10 3/4" |
| 6" | 11 1/2" | 12 | 1" | 14" |
| 8" | 13 3/4" | 12 | 1 1/8" | 16 1/2" |
| 10" | 17" | 16 | 1 1/4" | 20" |
| 12" | 19 1/4" | 20 | 1 1/4" | 22" |
| 14" | 20 3/4" | 20 | 1 3/8" | 23 3/4" |
| ANSI 900# |
| Pipe NB | Bolt PCD | No. of Bolts | Bolt Size | Flange OD |
| 2" * | 6 1/2" | 8 | 7/8" | 8 1/2" |
| 4" | 9 1/4" | 8 | 1 1/8" | 11 1/2" |
| 6" | 12 1/2" | 12 | 1 1/8" | 15" |
| 8" | 15 1/2" | 12 | 1 3/8" | 18 1/2" |
| 10" | 18 1/2" | 16 | 1 3/8" | 21 1/2" |
| 12" | 21" | 20 | 1 3/8" | 24" |
| 14" | 22" | 20 | 1 1/2" | 25 1/4" |
| * 2" Class 1500 is used for 2" Class 900 |
| ANSI 1500# |
| Pipe NB | Bolt PCD | No. of Bolts | Bolt Size | Flange OD |
| 2" | 6 1/2" | 8 | 7/8" | 8 1/2" |
| 4" | 9 1/2" | 8 | 1 1/4" | 12 1/4" |
| 6" | 12 1/2" | 12 | 1 3/8" | 15 1/2" |
| 8" | 15 1/2" | 12 | 1 5/8" | 19" |
