ASME B16.5 Class 300 Flanges — Dimensions by NPS
Class 300 flanges per ASME B16.5 are rated to 51.1 bar (740 psi) at ambient temperature for Group 1.1 materials (carbon steel). The table below lists all NPS sizes with flange OD, bolt circle diameter (BCD), bolt count, and minimum neck thickness. Click any row to view the full dimension table including metric equivalents.
| NPS | DN | OD (in) | OD (mm) | BCD (in) | Bolts | Bolt Size | Min Thk (in) | |
|---|---|---|---|---|---|---|---|---|
| NPS 1/2" | DN 15 | 3.75" | 95.3 | 2.62" | 4 | 1/2" | 0.56" | Full dims → |
| NPS 3/4" | DN 20 | 4.62" | 117.3 | 3.25" | 4 | 5/8" | 0.62" | Full dims → |
| NPS 1" | DN 25 | 4.88" | 124.0 | 3.50" | 4 | 5/8" | 0.69" | Full dims → |
| NPS 1-1/4" | DN 32 | 5.25" | 133.3 | 3.88" | 4 | 5/8" | 0.81" | Full dims → |
| NPS 1-1/2" | DN 40 | 6.12" | 155.4 | 4.50" | 4 | 3/4" | 0.88" | Full dims → |
| NPS 2" | DN 50 | 6.50" | 165.1 | 5.00" | 8 | 5/8" | 1.00" | Full dims → |
| NPS 2-1/2" | DN 65 | 7.50" | 190.5 | 5.88" | 8 | 3/4" | 1.12" | Full dims → |
| NPS 3" | DN 80 | 8.25" | 209.5 | 6.62" | 8 | 3/4" | 1.25" | Full dims → |
| NPS 4" | DN 100 | 10.75" | 273.1 | 8.50" | 8 | 3/4" | 1.50" | Full dims → |
| NPS 6" | DN 150 | 14.00" | 355.6 | 11.50" | 12 | 3/4" | 1.88" | Full dims → |
| NPS 8" | DN 200 | 16.50" | 419.1 | 13.75" | 12 | 7/8" | 2.00" | Full dims → |
| NPS 10" | DN 250 | 20.00" | 508.0 | 17.00" | 16 | 1" | 2.19" | Full dims → |
| NPS 12" | DN 300 | 22.00" | 558.8 | 19.25" | 16 | 1-1/8" | 2.50" | Full dims → |
Common Materials for Class 300
Class 300 flanges are commonly produced in ASTM A105 (carbon steel, forged),ASTM A182 F304 / F316L (austenitic stainless steel), andASTM A182 F11 / F22 (chrome-moly alloy steel) for elevated temperature service. The appropriate material depends on the fluid, design temperature, and corrosion environment. Use the Flange Weight Calculator to estimate unit weights for procurement or shipping.