1-1/2 inch Class 150 flange dimensions
ASME B16.5 Class 150 flange dimensions for 1-1/2 inch (DN 40) 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 | 1-1/2" (DN 40) |
| Pipe OD (bore end) | 48.3 mm |
| Flange outside diameter | 125 mm (4.92 in) |
| Minimum thickness (incl. 1.6 mm RF) | 15.9 mm (0.63 in) |
| Bolt circle diameter (PCD) | 98.4 mm (3.87 in) |
| Number of bolt holes | 4 |
| Bolt hole diameter | 0.62 in (15.7 mm) |
| Stud bolt diameter | 1/2" UNC |
| Raised face height | 1.6 mm (1/16 in) |
A complete 1-1/2" Class 150 joint needs 4 stud bolts of 1/2" diameter with 8 heavy hex nuts and one gasket.
Class 150 vs Class 300 — 1-1/2"
| Dimension | Class 150 | Class 300 |
|---|---|---|
| OD | 125 mm | 155 mm |
| Thickness | 15.9 mm | 19.1 mm |
| Bolt circle | 98.4 mm | 114.3 mm |
| Bolts | 4 × 1/2" | 4 × 3/4" |
Class 150 and Class 300 flanges do not bolt together — see 1-1/2" Class 300.
Frequently asked questions
What is the OD of a 1-1/2 inch Class 150 flange?
125 mm (4.92 in) per ASME B16.5.
How many bolts does a 1-1/2 inch Class 150 flange have?
4 bolts of 1/2 inch diameter in 0.62 inch holes on a 98.4 mm bolt circle.
What is the thickness of a 1-1/2 inch Class 150 flange?
The minimum flange thickness is 15.9 mm, including the 1.6 mm raised face.
Last updated 2026-11-02