Complete Flange Technical Data
The definitive reference for ASME B16.5 (NPS 1/2 - 24) and ASME B16.47 (NPS 26 - 60). Includes dimensions, bolt circles, drilling templates, and blind flange thicknesses.
Standard Flanges (B16.5)
NPS 1/2 to NPS 24. The most common industrial standard.
Class 150-2500
Large Diameter (B16.47)
NPS 26 to NPS 60. Critical Series A vs B distinction.
Series A / B
Technical Data
Bolting patterns, stud lengths, and torque requirements.
Engineering
Class 150 Dimensions
Standard Raised Face height is 1/16" (1.6mm). Dimensions in Inches.
| NPS | O.D. | Bolt Circle | # Bolts | Bolt Dia. | Hole Dia. | Thick (Min) Inc. RF |
|---|---|---|---|---|---|---|
| 1/2 | 3.50 | 2.38 | 4 | 1/2 | 5/8 | 0.44 |
| 3/4 | 3.88 | 2.75 | 4 | 1/2 | 5/8 | 0.50 |
| 1 | 4.25 | 3.12 | 4 | 1/2 | 5/8 | 0.56 |
| 1-1/4 | 4.62 | 3.50 | 4 | 1/2 | 5/8 | 0.62 |
| 1-1/2 | 5.00 | 3.88 | 4 | 1/2 | 5/8 | 0.69 |
| 2 | 6.00 | 4.75 | 4 | 5/8 | 3/4 | 0.75 |
| 2-1/2 | 7.00 | 5.50 | 4 | 5/8 | 3/4 | 0.88 |
| 3 | 7.50 | 6.00 | 4 | 5/8 | 3/4 | 0.94 |
| 3-1/2 | 8.50 | 7.00 | 8 | 5/8 | 3/4 | 0.94 |
| 4 | 9.00 | 7.50 | 8 | 5/8 | 3/4 | 0.94 |
| 5 | 10.00 | 8.50 | 8 | 3/4 | 7/8 | 0.94 |
| 6 | 11.00 | 9.50 | 8 | 3/4 | 7/8 | 1.00 |
| 8 | 13.50 | 11.75 | 8 | 3/4 | 7/8 | 1.12 |
| 10 | 16.00 | 14.25 | 12 | 7/8 | 1 | 1.19 |
| 12 | 19.00 | 17.00 | 12 | 7/8 | 1 | 1.25 |
| 14 | 21.00 | 18.75 | 12 | 1 | 1-1/8 | 1.38 |
| 16 | 23.50 | 21.25 | 16 | 1 | 1-1/8 | 1.44 |
| 18 | 25.00 | 22.75 | 16 | 1-1/8 | 1-1/4 | 1.56 |
| 20 | 27.50 | 25.00 | 20 | 1-1/8 | 1-1/4 | 1.69 |
| 24 | 32.00 | 29.50 | 20 | 1-1/4 | 1-3/8 | 1.88 |
Class 300 Dimensions
| NPS | O.D. | Bolt Circle | # Bolts | Bolt Dia. | Hole Dia. | Thick (Min) Inc. RF |
|---|---|---|---|---|---|---|
| 1/2 | 3.75 | 2.62 | 4 | 1/2 | 5/8 | 0.56 |
| 3/4 | 4.62 | 3.25 | 4 | 5/8 | 3/4 | 0.62 |
| 1 | 4.88 | 3.50 | 4 | 5/8 | 3/4 | 0.69 |
| 1-1/4 | 5.25 | 3.88 | 4 | 5/8 | 3/4 | 0.75 |
| 1-1/2 | 6.12 | 4.50 | 4 | 3/4 | 7/8 | 0.81 |
| 2 | 6.50 | 5.00 | 8 | 5/8 | 3/4 | 0.88 |
| 2-1/2 | 7.50 | 5.88 | 8 | 3/4 | 7/8 | 1.00 |
| 3 | 8.25 | 6.62 | 8 | 3/4 | 7/8 | 1.12 |
| 4 | 10.00 | 7.88 | 8 | 3/4 | 7/8 | 1.25 |
| 6 | 12.50 | 10.62 | 12 | 3/4 | 7/8 | 1.44 |
| 8 | 15.00 | 13.00 | 12 | 7/8 | 1 | 1.62 |
| 10 | 17.50 | 15.25 | 16 | 1 | 1-1/8 | 1.88 |
| 12 | 20.50 | 17.75 | 16 | 1-1/8 | 1-1/4 | 2.00 |
| 14 | 23.00 | 20.25 | 20 | 1-1/8 | 1-1/4 | 2.12 |
| 16 | 25.50 | 22.50 | 20 | 1-1/4 | 1-3/8 | 2.25 |
| 24 | 36.00 | 32.00 | 24 | 1-1/2 | 1-5/8 | 2.75 |
Class 600 Dimensions
From Class 400+, standard RF height is 1/4" (6.4mm). Thickness usually excludes this height.
| NPS | O.D. | Bolt Circle | # Bolts | Bolt Dia. | Hole Dia. | Thick Excl. RF |
|---|---|---|---|---|---|---|
| 1/2 | 3.75 | 2.62 | 4 | 1/2 | 5/8 | 0.56 |
| 3/4 | 4.62 | 3.25 | 4 | 5/8 | 3/4 | 0.62 |
| 1 | 4.88 | 3.50 | 4 | 5/8 | 3/4 | 0.69 |
| 2 | 6.50 | 5.00 | 8 | 5/8 | 3/4 | 1.00 |
| 3 | 8.25 | 6.62 | 8 | 3/4 | 7/8 | 1.25 |
| 4 | 10.75 | 8.50 | 8 | 7/8 | 1 | 1.50 |
| 6 | 14.00 | 11.50 | 12 | 1 | 1-1/8 | 1.88 |
| 8 | 16.50 | 13.75 | 12 | 1-1/8 | 1-1/4 | 2.19 |
| 10 | 20.00 | 17.00 | 16 | 1-1/4 | 1-3/8 | 2.50 |
| 12 | 22.00 | 19.25 | 20 | 1-1/4 | 1-3/8 | 2.62 |
| 24 | 37.00 | 33.00 | 24 | 1-7/8 | 2 | 4.00 |
Class 900 Dimensions
NPS 1/2 through 2-1/2 dimensions are identical to Class 1500.
| NPS | O.D. | Bolt Circle | # Bolts | Bolt Dia. | Hole Dia. | Thick Excl. RF |
|---|---|---|---|---|---|---|
| 3 | 9.50 | 7.50 | 8 | 7/8 | 1 | 1.50 |
| 4 | 11.50 | 9.25 | 8 | 1-1/8 | 1-1/4 | 1.75 |
| 6 | 15.00 | 12.50 | 12 | 1-1/8 | 1-1/4 | 2.19 |
| 8 | 18.50 | 15.50 | 12 | 1-3/8 | 1-1/2 | 2.50 |
| 10 | 21.50 | 18.50 | 16 | 1-3/8 | 1-1/2 | 2.75 |
| 12 | 24.00 | 21.00 | 20 | 1-3/8 | 1-1/2 | 3.12 |
| 24 | 41.00 | 35.50 | 20 | 2-1/2 | 2-5/8 | 5.50 |
Class 1500 Dimensions
| NPS | O.D. | Bolt Circle | # Bolts | Bolt Dia. | Hole Dia. | Thick Excl. RF |
|---|---|---|---|---|---|---|
| 1/2 | 4.75 | 3.25 | 4 | 3/4 | 7/8 | 0.88 |
| 1 | 5.88 | 4.00 | 4 | 7/8 | 1 | 1.12 |
| 2 | 8.50 | 6.50 | 8 | 7/8 | 1 | 1.50 |
| 3 | 10.50 | 8.00 | 8 | 1-1/8 | 1-1/4 | 1.88 |
| 4 | 12.25 | 9.50 | 8 | 1-1/4 | 1-3/8 | 2.12 |
| 6 | 15.50 | 12.50 | 12 | 1-3/8 | 1-1/2 | 3.25 |
| 8 | 19.00 | 15.50 | 12 | 1-5/8 | 1-3/4 | 3.62 |
| 10 | 23.00 | 19.00 | 12 | 1-7/8 | 2 | 4.25 |
| 12 | 26.50 | 22.50 | 16 | 2 | 2-1/8 | 4.88 |
| 24 | 46.00 | 39.00 | 16 | 3-1/2 | 3-5/8 | 8.00 |
Class 2500 Dimensions
| NPS | O.D. | Bolt Circle | # Bolts | Bolt Dia. | Hole Dia. | Thick Excl. RF |
|---|---|---|---|---|---|---|
| 1/2 | 5.25 | 3.50 | 4 | 3/4 | 7/8 | 1.19 |
| 1 | 6.25 | 4.25 | 4 | 7/8 | 1 | 1.38 |
| 2 | 9.25 | 6.75 | 8 | 1 | 1-1/8 | 2.00 |
| 3 | 12.00 | 9.00 | 8 | 1-1/4 | 1-3/8 | 2.62 |
| 4 | 14.00 | 10.75 | 8 | 1-1/2 | 1-5/8 | 3.00 |
| 6 | 19.00 | 14.50 | 8 | 2 | 2-1/8 | 4.25 |
| 8 | 21.75 | 17.25 | 12 | 2 | 2-1/8 | 5.00 |
| 10 | 26.50 | 21.25 | 12 | 2-1/2 | 2-5/8 | 6.50 |
| 12 | 30.00 | 24.38 | 12 | 2-3/4 | 2-7/8 | 7.25 |
Blind Flange Thickness Chart
Thickness often differs from standard flanges to withstand center bending moment.
| NPS | 150# | 300# | 600# | 900# | 1500# | 2500# |
|---|---|---|---|---|---|---|
| 1/2 | 0.44 | 0.56 | 0.56 | * | 0.88 | 1.19 |
| 3/4 | 0.50 | 0.62 | 0.62 | * | 1.00 | 1.25 |
| 1 | 0.56 | 0.69 | 0.69 | * | 1.12 | 1.38 |
| 2 | 0.75 | 0.88 | 1.00 | * | 1.50 | 2.00 |
| 3 | 0.94 | 1.12 | 1.25 | 1.50 | 1.88 | 2.62 |
| 4 | 0.94 | 1.25 | 1.50 | 1.75 | 2.12 | 3.00 |
| 6 | 1.00 | 1.44 | 1.88 | 2.19 | 3.25 | 4.25 |
| 8 | 1.12 | 1.62 | 2.19 | 2.50 | 3.62 | 5.00 |
| 10 | 1.19 | 1.88 | 2.50 | 2.75 | 4.25 | 6.50 |
| 12 | 1.25 | 2.00 | 2.62 | 3.12 | 4.88 | 7.25 |
* Sizes 1/2 to 2-1/2 in Class 900 use Class 1500 dimensions.
ASME B16.47: Series A vs. Series B (Large Diameter)
⚠️ CRITICAL WARNING: Series A (MSS SP-44) and Series B (API 605) are NOT interchangeable. They have different bolt circles and hole quantities.
| Feature | Series A (MSS SP-44) | Series B (API 605) | Implication |
|---|---|---|---|
| Flange O.D. (Example NPS 30) | 38.75" | 34.94" | Series B is physically smaller/lighter. |
| Bolt Circle | 36.00" | 32.75" | Do not match. |
| No. of Bolts | 28 Bolts | 44 Bolts | Series B uses more, smaller bolts. |
| Typical Use | Offshore, Risers, Vessels | Long Pipelines | Check spec sheet carefully. |
Quick Reference Bolt Chart (Class 150)
| NPS | Total Bolts | Diameter | Stud Length (RF) | Wrench Size |
|---|---|---|---|---|
| 2 | 4 | 5/8" | 3-1/4" | 1-1/16" |
| 3 | 4 | 5/8" | 3-1/2" | 1-1/16" |
| 4 | 8 | 5/8" | 3-1/2" | 1-1/16" |
| 6 | 8 | 3/4" | 4" | 1-1/4" |
| 8 | 8 | 3/4" | 4-1/4" | 1-1/4" |
| 10 | 12 | 7/8" | 4-3/4" | 1-7/16" |
| 12 | 12 | 7/8" | 4-3/4" | 1-7/16" |