Reference Table
ANSI Flange Dimensions
ANSI/ASME B16.5 flange dimensions — face diameter, bolt circle, bolt holes, and bolt sizes for Class 150, 300, 600, and 900 flanges from DN15 to DN600.
5 min readUpdated July 2026
ANSI/ASME B16.5 Class 150 Flanges
| DN | NPS | Flange OD (mm) | Bolt circle (mm) | No. bolts | Bolt size |
|---|---|---|---|---|---|
| 15 | 1/2" | 89 | 60.3 | 4 | 1/2" |
| 25 | 1" | 108 | 79.4 | 4 | 1/2" |
| 50 | 2" | 152 | 120.7 | 4 | 5/8" |
| 80 | 3" | 190 | 152.4 | 4 | 5/8" |
| 100 | 4" | 229 | 190.5 | 8 | 5/8" |
| 150 | 6" | 279 | 241.3 | 8 | 3/4" |
| 200 | 8" | 343 | 298.5 | 8 | 3/4" |
| 250 | 10" | 406 | 362.0 | 12 | 7/8" |
| 300 | 12" | 483 | 431.8 | 12 | 7/8" |
ANSI/ASME B16.5 Class 300 Flanges
| DN | NPS | Flange OD (mm) | Bolt circle (mm) | No. bolts | Bolt size |
|---|---|---|---|---|---|
| 15 | 1/2" | 95 | 66.5 | 4 | 1/2" |
| 25 | 1" | 124 | 82.6 | 4 | 5/8" |
| 50 | 2" | 165 | 127.0 | 8 | 5/8" |
| 80 | 3" | 210 | 168.3 | 8 | 3/4" |
| 100 | 4" | 254 | 200.0 | 8 | 3/4" |
| 150 | 6" | 318 | 269.9 | 12 | 3/4" |
| 200 | 8" | 381 | 330.2 | 12 | 7/8" |
| 250 | 10" | 444 | 387.4 | 16 | 1" |
| 300 | 12" | 521 | 450.9 | 16 | 1 1/8" |
Pressure-Temperature Ratings
| Class | Max pressure at 38°C (bar) | Max pressure at 200°C (bar) | Max pressure at 400°C (bar) |
|---|---|---|---|
| 150 | 19.6 | 13.8 | 5.5 |
| 300 | 51.1 | 43.9 | 30.9 |
| 600 | 102.1 | 87.9 | 61.9 |
| 900 | 153.2 | 131.6 | 92.8 |
| 1500 | 255.3 | 219.6 | 154.6 |
| 2500 | 425.5 | 366.4 | 257.6 |
How CHI can help
Ask CHI about flange dimensions and to recommend the correct flange class for your pressure and temperature. The CHI assistant can look up specific values, explain what each table entry means, and help you cross-reference between different standards and unit systems.