ASME B16.5 Flange Dimension Chart
Bolt circle, bolt count, bolt size, and flange OD for raised-face Class 150 and Class 300 flanges. Plus the pressure rating ladder for 150# through 2500#.
Class 150 Flanges
| NPS | Flange OD (in) | Bolt Circle (in) | # 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" |
| 5" | 10.00 | 8.50 | 8 | 3/4" |
| 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" |
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Class 300 Flanges
| NPS | Flange OD (in) | Bolt Circle (in) | # Bolts | Bolt size |
|---|---|---|---|---|
| 1/2" | 3.75 | 2.62 | 4 | 1/2" |
| 3/4" | 4.62 | 3.25 | 4 | 5/8" |
| 1" | 4.88 | 3.50 | 4 | 5/8" |
| 1-1/4" | 5.25 | 3.88 | 4 | 5/8" |
| 1-1/2" | 6.12 | 4.50 | 4 | 3/4" |
| 2" | 6.50 | 5.00 | 8 | 5/8" |
| 2-1/2" | 7.50 | 5.88 | 8 | 3/4" |
| 3" | 8.25 | 6.62 | 8 | 3/4" |
| 4" | 10.00 | 7.88 | 8 | 3/4" |
| 5" | 11.00 | 9.25 | 8 | 3/4" |
| 6" | 12.50 | 10.62 | 12 | 3/4" |
| 8" | 15.00 | 13.00 | 12 | 7/8" |
| 10" | 17.50 | 15.25 | 16 | 1" |
| 12" | 20.50 | 17.75 | 16 | 1-1/8" |
| 14" | 23.00 | 20.25 | 20 | 1-1/8" |
| 16" | 25.50 | 22.50 | 20 | 1-1/4" |
| 18" | 28.00 | 24.75 | 24 | 1-1/4" |
| 20" | 30.50 | 27.00 | 24 | 1-1/4" |
| 24" | 36.00 | 32.00 | 24 | 1-1/2" |
Class Pressure Rating Ladder (Group 1.1 Carbon Steel, A105)
Maximum allowable working pressure (psig) at temperature, from ASME B16.5 Table 2-1.1. Class numbers (150, 300, 600, etc.) are nominal — actual ratings depend on temperature.
| Temp | 150# | 300# | 600# | 900# | 1500# | 2500# |
|---|---|---|---|---|---|---|
| -20 to 100°F | 285 | 740 | 1,480 | 2,220 | 3,705 | 6,170 |
| 200°F | 260 | 675 | 1,350 | 2,025 | 3,375 | 5,625 |
| 300°F | 230 | 655 | 1,315 | 1,970 | 3,280 | 5,470 |
| 400°F | 200 | 635 | 1,270 | 1,900 | 3,170 | 5,280 |
| 500°F | 170 | 600 | 1,200 | 1,795 | 2,995 | 4,990 |
| 600°F | 140 | 550 | 1,095 | 1,640 | 2,735 | 4,560 |
| 700°F | 110 | 535 | 1,065 | 1,600 | 2,665 | 4,440 |
| 800°F | 80 | 410 | 825 | 1,235 | 2,055 | 3,430 |
Stainless and alloy materials have different rating ladders — see ASME B16.5 Tables 2-2.x for B8M/B16 etc.