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Engineering ToolBox > Carbon and Stainless Steel Flanges - ASME/ANSI Class 150
ASME/ANSI B16.5-1996 Pipe Flanges and Flanged Fittings - Class 150 Flanges - outside and inside diameters, bolt circles, numbers and diameters of bolts for Weld neck, Threaded, Slip-on, Lap joint, Socket weld and Blind flanges.
Carbon and stainless steel qualities according ASME B16.5 Table 1A.
| Pipe Size (inches) | Outside Diameter (inches) | Inside Diameter (inches) | Number of Bolt Holes | Bolt Hole Diameter (inches) 1) | Bolt Circle (inches) |
| 1/2 | 3-1/2 | 0.88 | 4 | 5/8 | 2-3/8 |
| 3/4 | 3-7/8 | 1.09 | 4 | 5/8 | 2-3/4 |
| 1 | 4-1/4 | 1.36 | 4 | 5/8 | 3-1/8 |
| 1-1/4 | 4-5/8 | 1.70 | 4 | 5/8 | 3-1/2 |
| 1-1/2 | 5 | 1.95 | 4 | 5/8 | 3-7/8 |
| 2 | 6 | 2.44 | 4 | 3/4 | 4-3/4 |
| 2-1/2 | 7 | 2.94 | 4 | 3/4 | 5-1/2 |
| 3 | 7-1/2 | 3.57 | 4 | 3/4 | 6 |
| 3-1/2 | 8-1/2 | 4.07 | 8 | 3/4 | 7 |
| 4 | 9 | 4.60 | 8 | 3/4 | 7-1/2 |
| 5 | 10 | 5.66 | 8 | 7/8 | 8-1/2 |
| 6 | 11 | 6.72 | 8 | 7/8 | 9-1/2 |
| 8 | 13-1/2 | 8.72 | 8 | 7/8 | 11-3/4 |
| 10 | 16 | 10.88 | 12 | 1 | 14-1/4 |
| 12 | 19 | 12.88 | 12 | 1 | 17 |
| 14 | 21 | 14.14 | 12 | 1-1/8 | 18-3/4 |
| 16 | 23-1/2 | 16.16 | 16 | 1-1/8 | 21-1/4 |
| 18 | 25 | 18.18 | 16 | 1-1/4 | 22-3/4 |
| 20 | 27-1/2 | 20.20 | 20 | 1-1/4 | 25 |
| 24 | 32 | 24.25 | 20 | 1-3/8 | 29-1/2 |
1) Recommended bolts are 1/8 smaller than the nominal bolt hole diameters shown.