ASME B16.5 Flange Dimensions Chart (Class 150 and 300)
Look up the outside diameter, bolt circle diameter, number of bolts and bolt size of ASME B16.5 Class 150 and Class 300 flanges, in inches and millimetres.
Class 150 flanges (inches)
| NPS | Flange OD | Bolt circle | Bolts | Bolt size |
|---|---|---|---|---|
| 1/2" | 3.50 | 2.38 | 4 | 1/2 |
| 3/4" | 3.88 | 2.75 | 4 | 1/2 |
| 1" | 4.25 | 3.12 | 4 | 1/2 |
| 1 1/4" | 4.62 | 3.50 | 4 | 1/2 |
| 1 1/2" | 5.00 | 3.88 | 4 | 1/2 |
| 2" | 6.00 | 4.75 | 4 | 5/8 |
| 2 1/2" | 7.00 | 5.50 | 4 | 5/8 |
| 3" | 7.50 | 6.00 | 4 | 5/8 |
| 4" | 9.00 | 7.50 | 8 | 5/8 |
| 6" | 11.00 | 9.50 | 8 | 3/4 |
| 8" | 13.50 | 11.75 | 8 | 3/4 |
| 10" | 16.00 | 14.25 | 12 | 7/8 |
| 12" | 19.00 | 17.00 | 12 | 7/8 |
| 14" | 21.00 | 18.75 | 12 | 1 |
| 16" | 23.50 | 21.25 | 16 | 1 |
| 18" | 25.00 | 22.75 | 16 | 1 1/8 |
| 20" | 27.50 | 25.00 | 20 | 1 1/8 |
| 24" | 32.00 | 29.50 | 20 | 1 1/4 |
Reading the Chart
Dimensions apply to raised face weld neck, slip on, socket weld, threaded and blind flanges of the same class and size. Data per ASME B16.5, cross checked against published manufacturer tables.
Worked example
A 4" Class 150 flange has a 9.00 in (228.6 mm) OD and 8 bolts of 5/8 in on a 7.50 in (190.5 mm) bolt circle.
Frequently Asked Questions
How many bolts does a 4 inch Class 150 flange have?
Eight bolts of 5/8 inch on a 7.50 inch bolt circle.
Do Class 150 and 300 flanges match?
No. Their bolt circles and usually bolt counts differ.
What is a bolt circle diameter?
The diameter of the circle through the centres of the bolt holes, also called PCD.
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