16 inch Class 300 flange dimensions
ASME B16.5 Class 300 flange dimensions for 16 inch (DN 400) 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 | 16" (DN 400) |
| Pipe OD (bore end) | 406.4 mm |
| Flange outside diameter | 650 mm (25.59 in) |
| Minimum thickness (incl. 1.6 mm RF) | 55.6 mm (2.19 in) |
| Bolt circle diameter (PCD) | 571.5 mm (22.50 in) |
| Number of bolt holes | 20 |
| Bolt hole diameter | 1.38 in (35.1 mm) |
| Stud bolt diameter | 1-1/4" UNC |
| Raised face height | 1.6 mm (1/16 in) |
A complete 16" Class 300 joint needs 20 stud bolts of 1-1/4" diameter with 40 heavy hex nuts and one gasket.
Class 300 vs Class 150 — 16"
| Dimension | Class 300 | Class 150 |
|---|---|---|
| OD | 650 mm | 595 mm |
| Thickness | 55.6 mm | 35.0 mm |
| Bolt circle | 571.5 mm | 539.8 mm |
| Bolts | 20 × 1-1/4" | 16 × 1" |
Class 300 and Class 150 flanges do not bolt together — see 16" Class 150.
Frequently asked questions
What is the OD of a 16 inch Class 300 flange?
650 mm (25.59 in) per ASME B16.5.
How many bolts does a 16 inch Class 300 flange have?
20 bolts of 1-1/4 inch diameter in 1.38 inch holes on a 571.5 mm bolt circle.
What is the thickness of a 16 inch Class 300 flange?
The minimum flange thickness is 55.6 mm, including the 1.6 mm raised face.
Last updated 2026-11-02