Stud bolts are the standard fasteners used to connect flanged joints in piping systems. The correct bolt diameter, length, and quantity depend on the flange size (NPS) and pressure class. The tables below provide stud bolt dimensions for ASME B16.5 raised face (RF) flanges from Class 150 through Class 2500, based on standard flange thicknesses and gasket allowances.
Class 150 Stud Bolt Chart
| NPS | Stud Bolt Dia (in) | Number of Bolts | Stud Bolt Length (in) | Stud Bolt Length (mm) |
|---|
| 1/2” | 1/2 | 4 | 3.50 | 89 |
| 3/4” | 1/2 | 4 | 3.75 | 95 |
| 1” | 1/2 | 4 | 3.75 | 95 |
| 1-1/4” | 1/2 | 4 | 4.00 | 102 |
| 1-1/2” | 1/2 | 4 | 4.00 | 102 |
| 2” | 5/8 | 4 | 4.25 | 108 |
| 2-1/2” | 5/8 | 4 | 4.50 | 114 |
| 3” | 5/8 | 4 | 4.50 | 114 |
| 3-1/2” | 5/8 | 8 | 4.50 | 114 |
| 4” | 5/8 | 8 | 4.50 | 114 |
| 5” | 3/4 | 8 | 5.00 | 127 |
| 6” | 3/4 | 8 | 5.00 | 127 |
| 8” | 3/4 | 8 | 5.25 | 133 |
| 10” | 7/8 | 12 | 5.50 | 140 |
| 12” | 7/8 | 12 | 5.50 | 140 |
| 14” | 1 | 12 | 6.25 | 159 |
| 16” | 1 | 16 | 6.50 | 165 |
| 18” | 1-1/8 | 16 | 7.00 | 178 |
| 20” | 1-1/8 | 20 | 7.25 | 184 |
| 24” | 1-1/4 | 20 | 8.00 | 203 |
Class 300 Stud Bolt Chart
| NPS | Stud Bolt Dia (in) | Number of Bolts | Stud Bolt Length (in) | Stud Bolt Length (mm) |
|---|
| 1/2” | 1/2 | 4 | 3.75 | 95 |
| 3/4” | 5/8 | 4 | 4.25 | 108 |
| 1” | 5/8 | 4 | 4.50 | 114 |
| 1-1/4” | 5/8 | 4 | 4.50 | 114 |
| 1-1/2” | 3/4 | 4 | 5.00 | 127 |
| 2” | 5/8 | 8 | 5.00 | 127 |
| 2-1/2” | 3/4 | 8 | 5.25 | 133 |
| 3” | 3/4 | 8 | 5.50 | 140 |
| 3-1/2” | 3/4 | 8 | 5.50 | 140 |
| 4” | 3/4 | 8 | 5.75 | 146 |
| 5” | 3/4 | 8 | 6.00 | 152 |
| 6” | 3/4 | 12 | 6.25 | 159 |
| 8” | 7/8 | 12 | 6.75 | 171 |
| 10” | 1 | 16 | 7.50 | 191 |
| 12” | 1-1/8 | 16 | 7.75 | 197 |
| 14” | 1-1/8 | 20 | 8.25 | 210 |
| 16” | 1-1/4 | 20 | 8.50 | 216 |
| 18” | 1-1/4 | 24 | 9.25 | 235 |
| 20” | 1-1/4 | 24 | 9.75 | 248 |
| 24” | 1-1/2 | 24 | 11.00 | 279 |
Class 600 Stud Bolt Chart
| NPS | Stud Bolt Dia (in) | Number of Bolts | Stud Bolt Length (in) | Stud Bolt Length (mm) |
|---|
| 1/2” | 1/2 | 4 | 3.75 | 95 |
| 3/4” | 5/8 | 4 | 4.25 | 108 |
| 1” | 5/8 | 4 | 4.50 | 114 |
| 1-1/4” | 5/8 | 4 | 4.75 | 121 |
| 1-1/2” | 3/4 | 4 | 5.25 | 133 |
| 2” | 5/8 | 8 | 5.25 | 133 |
| 2-1/2” | 3/4 | 8 | 5.50 | 140 |
| 3” | 3/4 | 8 | 5.75 | 146 |
| 3-1/2” | 7/8 | 8 | 6.25 | 159 |
| 4” | 7/8 | 8 | 6.50 | 165 |
| 5” | 1 | 8 | 7.25 | 184 |
| 6” | 1 | 12 | 7.50 | 191 |
| 8” | 1-1/8 | 12 | 8.50 | 216 |
| 10” | 1-1/4 | 16 | 9.50 | 241 |
| 12” | 1-3/8 | 20 | 10.00 | 254 |
| 14” | 1-3/8 | 20 | 10.75 | 273 |
| 16” | 1-1/2 | 20 | 11.50 | 292 |
| 18” | 1-5/8 | 20 | 12.50 | 318 |
| 20” | 1-5/8 | 24 | 13.00 | 330 |
| 24” | 1-7/8 | 24 | 15.00 | 381 |
Class 900 Stud Bolt Chart
| NPS | Stud Bolt Dia (in) | Number of Bolts | Stud Bolt Length (in) | Stud Bolt Length (mm) |
|---|
| 1/2” | 3/4 | 4 | 5.00 | 127 |
| 3/4” | 3/4 | 4 | 5.25 | 133 |
| 1” | 7/8 | 4 | 5.75 | 146 |
| 1-1/4” | 7/8 | 4 | 6.00 | 152 |
| 1-1/2” | 1 | 4 | 6.50 | 165 |
| 2” | 7/8 | 8 | 6.75 | 171 |
| 2-1/2” | 1 | 8 | 7.25 | 184 |
| 3” | 7/8 | 8 | 7.00 | 178 |
| 4” | 1-1/8 | 8 | 8.50 | 216 |
| 5” | 1-1/4 | 8 | 9.75 | 248 |
| 6” | 1-1/8 | 12 | 9.00 | 229 |
| 8” | 1-3/8 | 12 | 11.00 | 279 |
| 10” | 1-3/8 | 16 | 11.50 | 292 |
| 12” | 1-1/2 | 20 | 12.50 | 318 |
| 14” | 1-5/8 | 20 | 13.50 | 343 |
| 16” | 1-7/8 | 20 | 15.00 | 381 |
| 18” | 2 | 20 | 16.50 | 419 |
| 20” | 2 | 20 | 17.50 | 445 |
| 24” | 2-1/2 | 20 | 21.00 | 533 |
Class 1500 Stud Bolt Chart
| NPS | Stud Bolt Dia (in) | Number of Bolts | Stud Bolt Length (in) | Stud Bolt Length (mm) |
|---|
| 1/2” | 3/4 | 4 | 5.50 | 140 |
| 3/4” | 3/4 | 4 | 5.75 | 146 |
| 1” | 7/8 | 4 | 6.50 | 165 |
| 1-1/4” | 1 | 4 | 7.00 | 178 |
| 1-1/2” | 1 | 4 | 7.25 | 184 |
| 2” | 7/8 | 8 | 7.50 | 191 |
| 2-1/2” | 1 | 8 | 8.25 | 210 |
| 3” | 1-1/8 | 8 | 9.00 | 229 |
| 4” | 1-1/4 | 8 | 10.75 | 273 |
| 5” | 1-1/2 | 8 | 12.50 | 318 |
| 6” | 1-3/8 | 12 | 11.50 | 292 |
| 8” | 1-5/8 | 12 | 13.50 | 343 |
| 10” | 1-7/8 | 12 | 15.50 | 394 |
| 12” | 2 | 16 | 16.50 | 419 |
| 14” | 2-1/4 | 16 | 18.50 | 470 |
| 16” | 2-1/2 | 16 | 20.50 | 521 |
| 18” | 2-3/4 | 16 | 22.50 | 572 |
| 20” | 3 | 16 | 24.50 | 622 |
| 24” | 3-1/2 | 16 | 29.00 | 737 |
Class 2500 Stud Bolt Chart
| NPS | Stud Bolt Dia (in) | Number of Bolts | Stud Bolt Length (in) | Stud Bolt Length (mm) |
|---|
| 1/2” | 3/4 | 4 | 6.25 | 159 |
| 3/4” | 3/4 | 4 | 6.50 | 165 |
| 1” | 7/8 | 4 | 7.25 | 184 |
| 1-1/4” | 1 | 4 | 8.00 | 203 |
| 1-1/2” | 1-1/8 | 4 | 8.75 | 222 |
| 2” | 1 | 8 | 9.00 | 229 |
| 2-1/2” | 1-1/8 | 8 | 9.75 | 248 |
| 3” | 1-1/4 | 8 | 10.75 | 273 |
| 4” | 1-1/2 | 8 | 12.75 | 324 |
| 5” | 1-3/4 | 8 | 15.25 | 387 |
| 6” | 2 | 8 | 17.00 | 432 |
| 8” | 2-1/4 | 12 | 19.50 | 495 |
| 10” | 2-3/4 | 12 | 23.50 | 597 |
| 12” | 3 | 12 | 26.50 | 673 |
Notes
- Stud bolt lengths are calculated for raised face (RF) flanges and include allowances for two heavy hex nuts (ASME B18.2.2) and thread engagement.
- Standard bolt material is ASTM A193 Grade B7 (chromium-molybdenum alloy steel), paired with ASTM A194 Grade 2H heavy hex nuts.
- For ring-type joint (RTJ) flanges, stud bolt lengths are typically 1/4” (6 mm) shorter than RF flange values.
- For low-temperature service (below -29 C), use ASTM A320 Grade L7 studs with A194 Grade 4 or 7 nuts.
- For high-temperature service (above 500 C), consider ASTM A193 Grade B16 studs.
- All lengths are nominal and should be verified against the actual flange dimensions and gasket thickness for the specific application.
- Class 2500 flanges are defined in ASME B16.5 for sizes up to NPS 12” only.
- Bolt quantities and diameters are per ASME B16.5, Table 2.
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