Flange Dimensions Chart
ASME B16.5 raised-face flange dimensions in millimetres for Class 150, 300 and 600, NPS 1/2 to 24 — flange outside diameter, bolt circle diameter (PCD), number of bolt holes, bolt hole diameter and bolt size. Filter by NPS, DN or flange OD.
| NPS | DN | Flange OD (mm) | Raised face (mm) | Bolt circle PCD (mm) | No. of bolts | Bolt hole ⌀ (mm) | Bolt size (in) |
|---|---|---|---|---|---|---|---|
| 1/2 | 15 | 88.9 | 34.9 | 60.3 | 4 | 15.7 | 1/2 |
| 3/4 | 20 | 98.6 | 42.9 | 69.9 | 4 | 15.7 | 1/2 |
| 1 | 25 | 108.0 | 50.8 | 79.4 | 4 | 15.7 | 1/2 |
| 1 1/4 | 32 | 117.3 | 63.5 | 88.9 | 4 | 15.7 | 1/2 |
| 1 1/2 | 40 | 127.0 | 73.0 | 98.6 | 4 | 15.7 | 1/2 |
| 2 | 50 | 152.4 | 92.1 | 120.7 | 4 | 19.1 | 5/8 |
| 2 1/2 | 65 | 177.8 | 104.8 | 139.7 | 4 | 19.1 | 5/8 |
| 3 | 80 | 190.5 | 127.0 | 152.4 | 4 | 19.1 | 5/8 |
| 3 1/2 | 90 | 215.9 | 139.7 | 177.8 | 8 | 19.1 | 5/8 |
| 4 | 100 | 228.6 | 157.2 | 190.5 | 8 | 19.1 | 5/8 |
| 5 | 125 | 254.0 | 185.7 | 215.9 | 8 | 22.2 | 3/4 |
| 6 | 150 | 279.4 | 215.9 | 241.3 | 8 | 22.2 | 3/4 |
| 8 | 200 | 342.9 | 269.9 | 298.5 | 8 | 22.2 | 3/4 |
| 10 | 250 | 406.4 | 323.8 | 361.9 | 12 | 25.4 | 7/8 |
| 12 | 300 | 482.6 | 381.0 | 431.8 | 12 | 25.4 | 7/8 |
| 14 | 350 | 533.4 | 412.8 | 476.3 | 12 | 28.4 | 1 |
| 16 | 400 | 596.9 | 469.9 | 539.8 | 16 | 28.4 | 1 |
| 18 | 450 | 635.0 | 533.4 | 577.9 | 16 | 31.8 | 1 1/8 |
| 20 | 500 | 698.5 | 584.2 | 635.0 | 20 | 31.8 | 1 1/8 |
| 24 | 600 | 812.8 | 692.2 | 749.3 | 20 | 34.9 | 1 1/4 |
How to read the flange bolt hole pattern
Two numbers identify a flange bolt pattern: the bolt circle diameter (PCD) and the number of bolt holes. Holes are equally spaced on that circle and straddle the centreline of the pipe — for a 4-hole flange the holes sit at 45°, 135°, 225° and 315°, never on the vertical or horizontal axis. The bolt hole diameter is normally about 3 mm larger than the bolt for clearance.
Flanges of the same NPS but different pressure classes are not interchangeable: Class 300 and Class 600 flanges are heavier, with a larger OD, a larger PCD and bigger bolts than Class 150 for the same bore. Always confirm the class and facing before ordering mating flanges, studs and gaskets.
Dimensions shown are nominal ASME B16.5 values in millimetres for raised-face flanges, NPS 1/2 to 24. Confirm requirements against the governing standard and the manufacturer's data sheet before fabrication.
Related tools
- Flange Bolt Circle CalculatorChord distance and X/Y hole coordinates from the PCD.
- Flange Weight CalculatorEstimate flange weight in kg with bolt hole deduction.
- Flange Bolt Torque CalculatorTorque from target bolt load using the K-factor method.
- Gasket Area & Seating Load CalculatorRing gasket area and the bolt load needed to seat it.