6 inch Class 300 flange dimensions
ASME B16.5 Class 300 flange dimensions for 6 inch (DN 150) 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 | 6" (DN 150) |
| Pipe OD (bore end) | 168.3 mm |
| Flange outside diameter | 320 mm (12.60 in) |
| Minimum thickness (incl. 1.6 mm RF) | 35.0 mm (1.38 in) |
| Bolt circle diameter (PCD) | 269.9 mm (10.63 in) |
| Number of bolt holes | 12 |
| Bolt hole diameter | 0.88 in (22.4 mm) |
| Stud bolt diameter | 3/4" UNC |
| Raised face height | 1.6 mm (1/16 in) |
A complete 6" Class 300 joint needs 12 stud bolts of 3/4" diameter with 24 heavy hex nuts and one gasket.
Class 300 vs Class 150 — 6"
| Dimension | Class 300 | Class 150 |
|---|---|---|
| OD | 320 mm | 280 mm |
| Thickness | 35.0 mm | 23.9 mm |
| Bolt circle | 269.9 mm | 241.3 mm |
| Bolts | 12 × 3/4" | 8 × 3/4" |
Class 300 and Class 150 flanges do not bolt together — see 6" Class 150.
Frequently asked questions
What is the OD of a 6 inch Class 300 flange?
320 mm (12.60 in) per ASME B16.5.
How many bolts does a 6 inch Class 300 flange have?
12 bolts of 3/4 inch diameter in 0.88 inch holes on a 269.9 mm bolt circle.
What is the thickness of a 6 inch Class 300 flange?
The minimum flange thickness is 35.0 mm, including the 1.6 mm raised face.
Last updated 2026-11-02