12 inch Class 150 flange dimensions
ASME B16.5 Class 150 flange dimensions for 12 inch (DN 300) pipe. The same bolting dimensions apply to weld neck, slip-on, blind, socket weld, threaded and lap joint flanges of this size and class.
| Nominal size | 12" (DN 300) |
| Pipe OD (bore end) | 323.9 mm |
| Flange outside diameter | 485 mm (19.09 in) |
| Minimum thickness (incl. 1.6 mm RF) | 30.2 mm (1.19 in) |
| Bolt circle diameter (PCD) | 431.8 mm (17.00 in) |
| Number of bolt holes | 12 |
| Bolt hole diameter | 1.00 in (25.4 mm) |
| Stud bolt diameter | 7/8" UNC |
| Raised face height | 1.6 mm (1/16 in) |
A complete 12" Class 150 joint needs 12 stud bolts of 7/8" diameter with 24 heavy hex nuts and one gasket.
Class 150 vs Class 300 — 12"
| Dimension | Class 150 | Class 300 |
|---|---|---|
| OD | 485 mm | 520 mm |
| Thickness | 30.2 mm | 49.3 mm |
| Bolt circle | 431.8 mm | 450.8 mm |
| Bolts | 12 × 7/8" | 16 × 1-1/8" |
Class 150 and Class 300 flanges do not bolt together — see 12" Class 300.
Frequently asked questions
What is the OD of a 12 inch Class 150 flange?
485 mm (19.09 in) per ASME B16.5.
How many bolts does a 12 inch Class 150 flange have?
12 bolts of 7/8 inch diameter in 1.00 inch holes on a 431.8 mm bolt circle.
What is the thickness of a 12 inch Class 150 flange?
The minimum flange thickness is 30.2 mm, including the 1.6 mm raised face.
Last updated 2026-11-02