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This flange dimensions chart provides ASME B16.5 pipe flange dimensions for Class 150, 300, 600, 900, and 1500. Use the flange size charts to check key measurements, including outside diameter, flange thickness, bolt circle diameter, and bolt hole dimensions.
The ASME B16.5 standard covers pipe flanges and flanged fittings. The dimensional tables in this section detail key parameters such as Nominal Pipe Size (NPS), Outside Diameter (O.D.), Flange Thickness (Thk.), Bolt Circle Diameter (B.C.D.), and bolt hole configurations.
To ensure accurate reference, the dimensions are categorized into separate subsections by pressure class. The specific applicability, structural variations, and dimensions for each class are detailed below.
Standard Specification: ASME B16.5 / ASTM A/SA-105
Flange Type: Threaded Flange (NPT / BSPT Tapped)
Unit System: Imperial (Inch / Pounds)
| Nominal Pipe Size (NPS) | Outside Diam. of Flange (O) | Thick. of Flange (C) | Diam. of Raised Face (R) | Diam. of Hub at Base (X) | Length thru Hub (Y) | Min. Thread Length (T) | Min. Counter Bore (Q) | No. of Holes | Diam. of Holes | Diam. of Bolts | Diam. of Bolt Circle | Approx. Weight (Pounds) |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| ½ | 3.5 | 0.44 | 1.38 | 1.19 | 0.62 | 0.62 | — | 4 | 0.62 | 0.5 | 2.38 | 1 |
| ¾ | 3.88 | 0.5 | 1.69 | 1.5 | 0.62 | 0.62 | — | 4 | 0.62 | 0.5 | 2.75 | 2 |
| 1 | 4.25 | 0.56 | 2 | 1.94 | 0.69 | 0.69 | — | 4 | 0.62 | 0.5 | 3.12 | 2 |
| 1 ¼ | 4.62 | 0.62 | 2.5 | 2.31 | 0.81 | 0.81 | — | 4 | 0.62 | 0.5 | 3.5 | 3 |
| 1 ½ | 5 | 0.69 | 2.88 | 2.56 | 0.88 | 0.88 | — | 4 | 0.62 | 0.5 | 3.88 | 3 |
| 2 | 6 | 0.75 | 3.62 | 3.06 | 1 | 1 | — | 4 | 0.75 | 0.62 | 4.75 | 5 |
| 2 ½ | 7 | 0.88 | 4.12 | 3.56 | 1.12 | 1.12 | — | 4 | 0.75 | 0.62 | 5.5 | 7 |
| 3 | 7.5 | 0.94 | 5 | 4.25 | 1.19 | 1.19 | — | 4 | 0.75 | 0.62 | 6 | 8 |
| 3 ½ | 8.5 | 0.94 | 5.5 | 4.81 | 1.25 | 1.25 | — | 8 | 0.75 | 0.62 | 7 | 11 |
| 4 | 9 | 0.94 | 6.19 | 5.31 | 1.31 | 1.31 | — | 8 | 0.75 | 0.62 | 7.5 | 13 |
| 5 | 10 | 0.94 | 7.31 | 6.44 | 1.44 | 1.44 | — | 8 | 0.88 | 0.75 | 8.5 | 15 |
| 6 | 11 | 1 | 8.5 | 7.56 | 1.56 | 1.56 | — | 8 | 0.88 | 0.75 | 9.5 | 19 |
| 8 | 13.5 | 1.12 | 10.62 | 9.69 | 1.75 | 1.75 | — | 8 | 0.88 | 0.75 | 11.75 | 30 |
| 10 | 16 | 1.19 | 12.75 | 12 | 1.94 | 1.94 | — | 12 | 1 | 0.88 | 14.25 | 43 |
| 12 | 19 | 1.25 | 15 | 14.38 | 2.19 | 2.19 | — | 12 | 1 | 0.88 | 17 | 64 |
| 14 | 21 | 1.38 | 16.25 | 15.75 | 2.25 | 2.25 | — | 12 | 1.12 | 1 | 18.75 | 90 |
| 16 | 23.5 | 1.44 | 18.5 | 18 | 2.5 | 2.5 | — | 16 | 1.12 | 1 | 21.25 | 98 |
| 18 | 25 | 1.56 | 21 | 19.88 | 2.69 | 2.69 | — | 16 | 1.25 | 1.13 | 22.75 | 130 |
| 20 | 27.5 | 1.69 | 23 | 22 | 2.88 | 2.88 | — | 20 | 1.25 | 1.12 | 25 | 165 |
| 24 | 32 | 1.88 | 27.25 | 26.12 | 3.25 | 3.25 | — | 20 | 1.38 | 1.25 | 29.5 | 220 |
| Nominal Pipe Size (NPS) | Outside Diam. of Flange (O) | Thick. of Flange (C) | Diam. of Raised Face (R) | Diam. of Hub at Base (X) | Length thru Hub (Y) | Min. Thread Length (T) | Min. Counter Bore (Q) | No. of Holes | Diam. of Holes | Diam. of Bolts | Diam. of Bolt Circle | Approx. Weight (Pounds) |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| ½ | 3.75 | 0.56 | 1.38 | 1.5 | 0.88 | 0.62 | 0.93 | 4 | 0.62 | 0.5 | 2.62 | 2 |
| ¾ | 4.62 | 0.62 | 1.69 | 1.88 | 1 | 0.62 | 1.14 | 4 | 0.75 | 0.62 | 3.25 | 3 |
| 1 | 4.88 | 0.69 | 2 | 2.12 | 1.06 | 0.69 | 1.41 | 4 | 0.75 | 0.62 | 3.5 | 3 |
| 1 ¼ | 5.25 | 0.75 | 2.5 | 2.5 | 1.06 | 0.81 | 1.75 | 4 | 0.75 | 0.62 | 3.88 | 4 |
| 1 ½ | 6.12 | 0.81 | 2.88 | 2.75 | 1.19 | 0.88 | 1.99 | 4 | 0.88 | 0.75 | 4.5 | 6 |
| 2 | 6.5 | 0.88 | 3.62 | 3.31 | 1.31 | 1.12 | 2.5 | 8 | 0.75 | 0.62 | 5 | 7 |
| 2 ½ | 7.5 | 1 | 4.12 | 3.94 | 1.5 | 1.25 | 3 | 8 | 0.88 | 0.75 | 5.88 | 10 |
| 3 | 8.25 | 1.12 | 5 | 4.62 | 1.69 | 1.25 | 3.63 | 8 | 0.88 | 0.75 | 6.62 | 13 |
| 3 ½ | 9 | 1.19 | 5.5 | 5.25 | 1.75 | 1.44 | 4.13 | 8 | 0.88 | 0.75 | 7.25 | 17 |
| 4 | 10 | 1.25 | 6.19 | 5.75 | 1.88 | 1.44 | 4.63 | 8 | 0.88 | 0.75 | 7.88 | 22 |
| 5 | 11 | 1.38 | 7.31 | 7 | 2 | 1.69 | 5.69 | 8 | 0.88 | 0.75 | 9.25 | 28 |
| 6 | 12.5 | 1.44 | 8.5 | 8.12 | 2.06 | 1.81 | 6.75 | 12 | 0.88 | 0.75 | 10.62 | 39 |
| 8 | 15 | 1.62 | 10.62 | 10.25 | 2.44 | 2 | 8.75 | 12 | 1 | 0.88 | 13 | 58 |
| 10 | 17.5 | 1.88 | 12.75 | 12.62 | 2.62 | 2.19 | 10.88 | 16 | 1.12 | 1 | 15.25 | 81 |
| 12 | 20.5 | 2 | 15 | 14.75 | 2.88 | 2.38 | 12.94 | 16 | 1.25 | 1.12 | 17.75 | 115 |
| 14 | 23 | 2.12 | 16.25 | 16.75 | 3 | 2.5 | 14.19 | 20 | 1.25 | 1.12 | 20.25 | 165 |
| 16 | 25.5 | 2.25 | 18.5 | 19 | 3.25 | 2.69 | 16.19 | 20 | 1.38 | 1.25 | 22.5 | 190 |
| 18 | 28 | 2.38 | 21 | 21 | 3.5 | 2.75 | 18.19 | 24 | 1.38 | 1.25 | 24.75 | 250 |
| 20 | 30.5 | 2.5 | 23 | 23.12 | 3.75 | 2.88 | 20.19 | 24 | 1.38 | 1.25 | 27 | 315 |
| 24 | 36 | 2.75 | 27.25 | 27.62 | 4.19 | 3.25 | 24.19 | 24 | 1.62 | 1.5 | 32 | 475 |
| Nominal Pipe Size (NPS) | Outside Diam. of Flange (O) | Thick. of Flange (C) | Diam. of Raised Face (R) | Diam. of Hub at Base (X) | Length thru Hub (Y) | Min. Thread Length (T) | Min. Counter Bore (Q) | No. of Holes | Diam. of Holes | Diam. of Bolts | Diam. of Bolt Circle | Approx. Weight (Pounds) |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| ½ | 3.75 | 0.56 | 1.38 | 1.5 | 0.88 | 0.62 | 0.93 | 4 | 0.62 | 0.5 | 2.62 | 2 |
| ¾ | 4.62 | 0.62 | 1.69 | 1.88 | 1 | 0.62 | 1.14 | 4 | 0.75 | 0.62 | 3.25 | 3 |
| 1 | 4.88 | 0.69 | 2 | 2.12 | 1.06 | 0.69 | 1.41 | 4 | 0.75 | 0.62 | 3.5 | 4 |
| 1 ¼ | 5.25 | 0.81 | 2.5 | 2.5 | 1.12 | 0.81 | 1.75 | 4 | 0.75 | 0.62 | 3.88 | 5 |
| 1 ½ | 6.12 | 0.88 | 2.88 | 2.75 | 1.25 | 0.88 | 1.99 | 4 | 0.88 | 0.75 | 4.5 | 7 |
| 2 | 6.5 | 1 | 3.62 | 3.31 | 1.44 | 1.12 | 2.5 | 8 | 0.75 | 0.62 | 5 | 9 |
| 2 ½ | 7.5 | 1.12 | 4.12 | 3.94 | 1.62 | 1.25 | 3 | 8 | 0.88 | 0.75 | 5.88 | 13 |
| 3 | 8.25 | 1.25 | 5 | 4.62 | 1.81 | 1.38 | 3.63 | 8 | 0.88 | 0.75 | 6.62 | 16 |
| 3 ½ | 9 | 1.38 | 5.5 | 5.25 | 1.94 | 1.56 | 4.13 | 8 | 1 | 0.88 | 7.25 | 21 |
| 4 | 10.75 | 1.5 | 6.19 | 6 | 2.12 | 1.62 | 4.63 | 8 | 1 | 0.88 | 8.5 | 37 |
| 5 | 13 | 1.75 | 7.31 | 7.44 | 2.38 | 1.88 | 5.69 | 8 | 1.12 | 1 | 10.5 | 63 |
| 6 | 14 | 1.88 | 8.5 | 8.75 | 2.62 | 2 | 6.75 | 12 | 1.12 | 1 | 11.5 | 80 |
| 8 | 16.5 | 2.19 | 10.62 | 10.75 | 3 | 2.25 | 8.75 | 12 | 1.25 | 1.12 | 13.75 | 115 |
| 10 | 20 | 2.5 | 12.75 | 13.5 | 3.38 | 2.56 | 10.88 | 16 | 1.38 | 1.25 | 17 | 170 |
| 12 | 22 | 2.62 | 15 | 15.75 | 3.62 | 2.75 | 12.94 | 20 | 1.38 | 1.25 | 19.25 | 200 |
| 14 | 23.75 | 2.75 | 16.25 | 17 | 3.69 | 2.88 | 14.19 | 20 | 1.5 | 1.38 | 20.75 | 230 |
| 16 | 27 | 3 | 18.5 | 19.5 | 4.19 | 3.06 | 16.19 | 20 | 1.62 | 1.5 | 23.75 | 330 |
| 18 | 29.25 | 3.25 | 21 | 21.5 | 4.62 | 3.12 | 18.19 | 20 | 1.75 | 1.63 | 25.75 | 400 |
| 20 | 32 | 3.5 | 23 | 24 | 5 | 3.25 | 20.19 | 24 | 1.75 | 1.62 | 28.5 | 510 |
| 24 | 37 | 4 | 27.25 | 28.25 | 5.5 | 3.62 | 24.19 | 24 | 2 | 1.88 | 33 | 730 |
| Nominal Pipe Size (NPS) | Outside Diam. of Flange (O) | Thick. of Flange (C) | Diam. of Raised Face (R) | Diam. of Hub at Base (X) | Length thru Hub (Y) | Min. Thread Length (T) | Min. Counter Bore (Q) | No. of Holes | Diam. of Holes | Diam. of Bolts | Diam. of Bolt Circle | Approx. Weight (Pounds) |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| ½ | 4.75 | 0.88 | 1.38 | 1.5 | 1.25 | 0.88 | 0.93 | 4 | 0.88 | 0.75 | 3.25 | 4 |
| ¾ | 5.12 | 1 | 1.69 | 1.75 | 1.38 | 1 | 1.14 | 4 | 0.88 | 0.75 | 3.5 | 5 |
| 1 | 5.88 | 1.12 | 2 | 2.06 | 1.62 | 1.12 | 1.41 | 4 | 1 | 0.88 | 4 | 8 |
| 1 ¼ | 6.25 | 1.12 | 2.5 | 2.5 | 1.62 | 1.19 | 1.75 | 4 | 1 | 0.88 | 4.38 | 9 |
| 1 ½ | 7 | 1.25 | 2.88 | 2.75 | 1.75 | 1.25 | 1.99 | 4 | 1.12 | 1 | 4.88 | 12 |
| 2 | 8.5 | 1.5 | 3.62 | 4.12 | 2.25 | 1.5 | 2.5 | 8 | 1 | 0.88 | 6.5 | 25 |
| 2 ½ | 9.62 | 1.62 | 4.12 | 4.88 | 2.5 | 1.88 | 3 | 8 | 1.12 | 1 | 7.5 | 36 |
| 3 | 9.5 | 1.5 | 5 | 5 | 2.12 | 1.62 | 3.63 | 8 | 1 | 0.88 | 7.5 | 26 |
| 4 | 11.5 | 1.75 | 6.19 | 6.25 | 2.75 | 1.88 | 4.63 | 8 | 1.25 | 1.12 | 9.25 | 53 |
| 5 | 13.75 | 2 | 7.31 | 7.5 | 3.12 | 2.12 | 5.69 | 8 | 1.38 | 1.25 | 11 | 83 |
| 6 | 15 | 2.19 | 8.5 | 9.25 | 3.38 | 2.25 | 6.75 | 12 | 1.25 | 1.12 | 12.5 | 110 |
| 8 | 18.5 | 2.5 | 10.62 | 11.75 | 4 | 2.5 | 8.75 | 12 | 1.5 | 1.38 | 15.5 | 170 |
| 10 | 21.5 | 2.75 | 12.75 | 14.5 | 4.25 | 2.81 | 10.88 | 16 | 1.5 | 1.38 | 18.5 | 245 |
| 12 | 24 | 3.12 | 15 | 16.5 | 4.62 | 3 | 12.94 | 20 | 1.5 | 1.38 | 21 | 325 |
| 14 | 25.25 | 3.38 | 16.25 | 17.75 | 5.12 | 3.25 | 14.19 | 20 | 1.62 | 1.5 | 22 | 400 |
| 16 | 27.75 | 3.5 | 18.5 | 20 | 5.25 | 3.38 | 16.19 | 20 | 1.75 | 1.63 | 24.25 | 425 |
| 18 | 31 | 4 | 21 | 22.25 | 6 | 3.5 | 18.19 | 20 | 2 | 1.88 | 27 | 600 |
| 20 | 33.75 | 4.25 | 23 | 24.5 | 6.25 | 3.62 | 20.19 | 20 | 2.12 | 2 | 29.5 | 730 |
| 24 | 41 | 5.5 | 27.25 | 29.5 | 8 | 4 | 24.19 | 20 | 2.62 | 2.5 | 35.5 | 1400 |
| Nominal Pipe Size (NPS) | Outside Diam. of Flange (O) | Thick. of Flange (C) | Diam. of Raised Face (R) | Diam. of Hub at Base (X) | Length thru Hub (Y) | Min. Thread Length (T) | Min. Counter Bore (Q) | No. of Holes | Diam. of Holes | Diam. of Bolts | Diam. of Bolt Circle | Approx. Weight (Pounds) |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| ½ | 4.75 | 0.88 | 1.38 | 1.5 | 1.25 | 0.88 | 0.93 | 4 | 0.88 | 0.75 | 3.25 | 4 |
| ¾ | 5.12 | 1 | 1.69 | 1.75 | 1.38 | 1 | 1.14 | 4 | 0.88 | 0.75 | 3.5 | 5 |
| 1 | 5.88 | 1.12 | 2 | 2.06 | 1.62 | 1.12 | 1.41 | 4 | 1 | 0.88 | 4 | 8 |
| 1 ¼ | 6.25 | 1.12 | 2.5 | 2.5 | 1.62 | 1.19 | 1.75 | 4 | 1 | 0.88 | 4.38 | 9 |
| 1 ½ | 7 | 1.25 | 2.88 | 2.75 | 1.75 | 1.25 | 1.99 | 4 | 1.12 | 1 | 4.88 | 12 |
| 2 | 8.5 | 1.5 | 3.62 | 4.12 | 2.25 | 1.5 | 2.5 | 8 | 1 | 0.88 | 6.5 | 25 |
| 2 ½ | 9.62 | 1.62 | 4.12 | 4.88 | 2.5 | 1.88 | 3 | 8 | 1.12 | 1 | 7.5 | 36 |
| 3 | 10.5 | 1.88 | 5 | 5.25 | 2.62 | 2.19 | 3.63 | 8 | 1.25 | 1.12 | 8 | 52 |
| 4 | 12.25 | 2.12 | 6.19 | 6.38 | 3.06 | 2.5 | 4.63 | 8 | 1.38 | 1.25 | 9.5 | 81 |
| 5 | 14.75 | 2.88 | 7.31 | 7.75 | 4.19 | 3.25 | 5.69 | 8 | 1.62 | 1.5 | 11.5 | 155 |
| 6 | 15.5 | 3.12 | 8.5 | 8.75 | 4.62 | 3.5 | 6.75 | 8 | 1.75 | 1.62 | 12.5 | 185 |
| 8 | 19 | 3.62 | 10.62 | 11.12 | 5.38 | 4.19 | 8.75 | 12 | 1.75 | 1.62 | 15.5 | 315 |
| 10 | 23 | 4.25 | 12.75 | 13.75 | 6.38 | 4.75 | 10.88 | 12 | 2.12 | 2 | 19 | 550 |
| 12 | 26.5 | 4.88 | 15 | 16.25 | 7.25 | 5.38 | 12.94 | 16 | 2.38 | 2.25 | 22.5 | 790 |
| 14 | 29.5 | 5.25 | 16.25 | 17.75 | 7.75 | 5.75 | 14.19 | 16 | 2.62 | 2.5 | 25 | 1020 |
| 16 | 32.5 | 5.75 | 18.5 | 20.25 | 8.5 | 6.25 | 16.19 | 16 | 2.88 | 2.75 | 27.5 | 1340 |
| 18 | 36 | 6.38 | 21 | 22.75 | 9.5 | 7 | 18.19 | 16 | 3.12 | 3 | 30.5 | 1840 |
| 20 | 38.75 | 7 | 23 | 25 | 10.5 | 7.75 | 20.19 | 16 | 3.38 | 3.25 | 32.75 | 2280 |
| 24 | 46 | 8 | 27.25 | 29.5 | 12 | 8.88 | 24.19 | 16 | 4 | 3.75 | 39 | 3600 |
Note: Dimensions are in inches. Weights are approximate and refer to the specified flange configuration and material.
A flange dimensions chart lists the key measurements used to identify flange sizes and check connection compatibility.
NPS (Nominal Pipe Size): The nominal pipe size designation, which is not the pipe's actual outside diameter.
Outside Diameter (O): The overall diameter of the flange.
Flange Thickness (C): The flange thickness specified in the dimensional table.
Bolt Circle Diameter (BCD): The diameter of the circle passing through the centers of the bolt holes.
Bolt Hole Size and Quantity: The diameter and number of bolt holes used to check alignment with the mating flange.
Raised Face Diameter (R): The diameter of the raised sealing face.
Download the flange dimensions chart PDF for an offline reference to ASME B16.5 flange dimensions across Class 150, 300, 600, 900 and 1500. The PDF includes the dimensional tables and measurement details for convenient engineering reference.
↓ Download Full PDF Datasheet (Eastern Steels)
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