4 inch Class 300 flange dimensions
ASME B16.5 Class 300 flange dimensions for 4 inch (DN 100) 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 | 4" (DN 100) |
| Pipe OD (bore end) | 114.3 mm |
| Flange outside diameter | 255 mm (10.04 in) |
| Minimum thickness (incl. 1.6 mm RF) | 30.2 mm (1.19 in) |
| Bolt circle diameter (PCD) | 200.0 mm (7.87 in) |
| Number of bolt holes | 8 |
| 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 4" Class 300 joint needs 8 stud bolts of 3/4" diameter with 16 heavy hex nuts and one gasket.
Class 300 vs Class 150 — 4"
| Dimension | Class 300 | Class 150 |
|---|---|---|
| OD | 255 mm | 230 mm |
| Thickness | 30.2 mm | 22.3 mm |
| Bolt circle | 200.0 mm | 190.5 mm |
| Bolts | 8 × 3/4" | 8 × 5/8" |
Class 300 and Class 150 flanges do not bolt together — see 4" Class 150.
Frequently asked questions
What is the OD of a 4 inch Class 300 flange?
255 mm (10.04 in) per ASME B16.5.
How many bolts does a 4 inch Class 300 flange have?
8 bolts of 3/4 inch diameter in 0.88 inch holes on a 200.0 mm bolt circle.
What is the thickness of a 4 inch Class 300 flange?
The minimum flange thickness is 30.2 mm, including the 1.6 mm raised face.
Last updated 2026-11-02