Weld neck flange dimensions are covered in ASME B16.5 – which covers Pipe Flanges and Flanged Fittings for size NPS ½” to 24” for above NPS 26” to 60” it should be as per ASME B16.47.

During a dimensional inspection of weld neck flange, you should check for

  • Outer & Inner Diameter of body
  • Bolt Circle & Bolt hole Diameter
  • the thickness of weld end
  • Length of the Hub and
  • Straightness and alignment of the bolt hole
weld neck flange dimensions

Class 150 Weld Neck Flange Dimensions

Size in Inch Size in mm Outer Diameter Flange Thickness Hub OD Weld Neck OD Welding Neck Length Bore RF Diameter RF Height PCD Weld Face
A B C D E F G H I J
1/2 15 90 9.6 30 21.3 46 Welding Neck bore is derived from the pipe schedule 34.9 2 60.3 1.6
3/4 20 100 11.2 38 26.7 51 42.9 2 69.9 1.6
1 25 110 12.7 49 33.4 54 50.8 2 79.4 1.6
1 1/4 32 115 14.3 59 42.2 56 63.5 2 88.9 1.6
1 1/2 40 125 15.9 65 48.3 60 73 2 98.4 1.6
2 50 150 17.5 78 60.3 62 92.1 2 120.7 1.6
2 1/2 65 180 20.7 90 73 68 104.8 2 139.7 1.6
3 80 190 22.3 108 88.9 68 127 2 152.4 1.6
3 1/2 90 215 22.3 122 101.6 70 139.7 2 177.8 1.6
4 100 230 22.3 135 114.3 75 157.2 2 190.5 1.6
5 125 255 22.3 164 141.3 87 185.7 2 215.9 1.6
6 150 280 23.9 192 168.3 87 215.9 2 241.3 1.6
8 200 345 27 246 219.1 100 269.9 2 298.5 1.6
10 250 405 28.6 305 273 100 323.8 2 362 1.6
12 300 485 30.2 365 323.8 113 381 2 431.8 1.6
14 350 535 33.4 400 355.6 125 412.8 2 476.3 1.6
16 400 595 35 457 406.4 125 469.9 2 539.8 1.6
18 450 635 38.1 505 457.2 138 533.4 2 577.9 1.6
20 500 700 41.3 559 508 143 584.2 2 635 1.6
24 600 815 46.1 663 610 151 692.2 2 749.3 1.6

Class 150 Weld Neck Flange Stud & Bolt Dimensions

Size in Inch Size in mm No of Bolts Bolt Size UNC Machine Bolt Length RF Stud Length Hole Size ISO Stud Size Weight in kg
1/2 15 4 1/2 50 55 5/8 M14 0.6
3/4 20 4 1/2 50 65 5/8 M14 0.9
1 25 4 1/2 55 65 5/8 M14 1.4
1 1/4 32 4 1/2 55 70 5/8 M14 1.4
1 1/2 40 4 1/2 65 70 5/8 M14 1.8
2 50 4 5/8 70 85 3/4 M16 2.7
2 1/2 65 4 5/8 75 90 3/4 M16 3.7
3 80 4 5/8 75 90 3/4 M16 4.6
3 1/2 90 8 5/8 75 90 3/4 M16 5.5
4 100 8 5/8 75 90 3/4 M16 6.8
5 125 8 3/4 85 95 7/8 M20 8.7
6 150 8 3/4 85 100 7/8 M20 10.9
8 200 8 3/4 90 110 7/8 M20 17.7
10 250 12 7/8 100 115 1 M24 24
12 300 12 7/8 100 120 1 M24 37
14 350 12 1 115 135 1 1/8 M27 50
16 400 16 1 115 135 1 1/8 M27 64
18 450 16 1 1/8 125 145 1 1/4 M30 68
20 500 20 1 1/8 140 160 1 1/4 M30 82
24 600 20 1 1/4 150 170 1 3/8 M33 118
Piping Courses

Class 300 Weld Neck Flange Dimensions

Size in Inch Size in mm Outer Diameter Flange Thickness Hub OD Weld Neck OD Welding Neck Length Bore RF Diameter RF Height PCD Weld Face
A B C D E F G H I J
1/2 15 95 12.7 38 21.3 51 Welding Neck bore is derived from the pipe schedule 34.9 2 66.7 1.6
3/4 20 115 14.3 48 26.7 56 42.9 2 82.6 1.6
1 25 125 15.9 54 33.4 60 50.8 2 88.9 1.6
1 1/4 32 135 17.5 64 42.2 64 63.5 2 98.4 1.6
1 1/2 40 155 19.1 70 48.3 67 73 2 114.3 1.6
2 50 165 20.7 84 60.3 68 92.1 2 127 1.6
2 1/2 65 190 23.9 100 73 75 104.8 2 149.2 1.6
3 80 210 27 117 88.9 78 127 2 168.3 1.6
3 1/2 90 230 28.6 133 101.6 79 139.7 2 184.2 1.6
4 100 255 30.2 146 114.3 84 157.2 2 200 1.6
5 125 280 33.4 178 141.3 97 185.7 2 235 1.6
6 150 320 35 206 168.3 97 215.9 2 269.9 1.6
8 200 380 39.7 260 219.1 110 269.9 2 330.2 1.6
10 250 445 46.1 321 273 116 323.8 2 387.4 1.6
12 300 520 49.3 375 323.8 129 381 2 450.8 1.6
14 350 585 52.4 425 355.6 141 412.8 2 514.4 1.6
16 400 650 55.6 483 406.4 144 469.9 2 571.5 1.6
18 450 710 58.8 533 457 157 533.4 2 628.6 1.6
20 500 775 62 587 508 160 584.2 2 685.8 1.6
24 600 915 68.3 702 610 167 692.2 2 812.8 1.6

Class 300 Weld Neck Flange Stud & Bolt Dimensions

Size in Inch Size in mm No of Bolts Bolt Size UNC Machine Bolt Length RF Stud Length Hole Size ISO Stud Size Weight in kg
1/2 15 4 1/2 55 65 5/8 M14 1.4
3/4 20 4 5/8 65 75 3/4 M16 1.4
1 25 4 5/8 65 75 3/4 M16 1.8
1 1/4 32 4 5/8 70 85 3/4 M16 2.3
1 1/2 40 4 3/4 75 90 7/8 M20 3.2
2 50 8 5/8 75 90 3/4 M16 4.1
2 1/2 65 8 3/4 85 100 7/8 M20 5.5
3 80 8 3/4 90 110 7/8 M20 6.8
3 1/2 90 8 3/4 95 110 7/8 M20 8.2
4 100 8 3/4 95 115 7/8 M20 11.4
5 125 8 3/4 110 120 7/8 M20 14.6
6 150 12 3/4 110 120 7/8 M20 19.1
8 200 12 7/8 120 140 1 M24 31
10 250 16 1 140 160 1 1/8 M27 42
12 300 16 1 1/8 145 170 1 1/4 M30 64
14 350 20 1 1/8 160 180 1 1/4 M30 82
16 400 20 1 1/4 165 190 1 3/8 M33 113
18 450 24 1 1/4 170 195 1 3/8 M33 145
20 500 24 1 1/4 185 205 1 3/8 M33 182
24 600 24 1 1/2 205 230 1 5/8 M39 264

Class 400 Weld Neck Flange Dimensions

Size in Inch Size in mm Outer Diameter Flange Thickness Hub OD Weld Neck OD Welding Neck Length Bore RF Diameter RF Height PCD Weld Face
A B C D E F G H I J
1/2 15 95 14.3 38 21.3 52 Welding Neck bore is derived from the pipe schedule 34.9 7 66.7 1.6
3/4 20 115 15.9 48 26.7 57 42.9 7 82.6 1.6
1 25 125 17.5 54 33.4 62 50.8 7 88.9 1.6
1 1/4 32 135 20.7 64 42.2 67 63.5 7 98.4 1.6
1 1/2 40 155 22.3 70 48.3 70 73 7 114.3 1.6
2 50 165 25.4 84 60.3 73 92.1 7 127 1.6
2 1/2 65 190 28.6 100 73 79 104.8 7 149.2 1.6
3 80 210 31.8 117 88.9 83 127 7 168.3 1.6
3 1/2 90 230 35 133 101.6 86 139.7 7 184.2 1.6
4 100 255 35 146 114.3 89 157.2 7 200 1.6
5 125 280 38.1 178 141.3 102 185.7 7 235 1.6
6 150 320 41.3 206 168.3 103 215.9 7 269.9 1.6
8 200 380 47.7 260 219.1 117 269.9 7 330 1.6
10 250 445 54 321 273 124 323.8 7 387.4 1.6
12 300 520 57.2 375 323.8 137 381 7 450.8 1.6
14 350 585 60.4 425 355.6 149 412.8 7 514.4 1.6
16 400 650 63.5 483 406.4 152 469.9 7 571.5 1.6
18 450 710 66.7 533 457 165 533.4 7 628.6 1.6
20 500 775 69.9 587 508 168 584.2 7 685.8 1.6
24 600 915 76.2 702 610 175 692.2 7 812.8 1.6

Class 400 Weld Neck Flange Stud & Bolt Dimensions

Size in Inch Size in mm No of Bolts Bolt Size UNC RF Stud Length Hole Size ISO Stud Size
1/2 15 4 1/2 75 5/8 M14
3/4 20 4 5/8 90 3/4 M16
1 25 4 5/8 90 3/4 M16
1 1/4 32 4 5/8 95 3/4 M16
1 1/2 40 4 3/4 110 7/8 M20
2 50 8 5/8 110 3/4 M16
2 1/2 65 8 3/4 120 7/8 M20
3 80 8 3/4 125 7/8 M20
3 1/2 90 8 7/8 140 1 M24
4 100 8 7/8 140 1 M24
5 125 8 7/8 145 1 M24
6 150 12 7/8 150 1 M24
8 200 12 1 170 1 1/8 M27
10 250 16 1 1/8 190 1 1/4 M30
12 300 16 1 1/4 205 1 3/8 M33
14 350 20 1 1/4 210 1 3/8 M33
16 400 20 1 3/8 220 1 1/2 M36
18 450 24 1 3/8 230 1 1/2 M36
20 500 24 1 1/2 240 1 3/4 M39
24 600 24 1 3/4 265 1 7/8 M45
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Class 600 Weld Neck Flange Dimensions

Size in Inch Size in mm Outer Diameter Flange Thickness Hub OD Weld Neck OD Welding Neck Length Bore RF Diameter RF Height PCD Weld Face
A B C D E F G H I J
1/2 15 95 14.3 38 21.3 52 Welding Neck bore is derived from the pipe schedule 34.9 7 66.7 1.6
3/4 20 115 15.9 48 26.7 57 42.9 7 82.6 1.6
1 25 125 17.5 54 33.4 62 50.8 7 88.9 1.6
1 1/4 32 135 20.7 64 42.2 67 63.5 7 98.4 1.6
1 1/2 40 155 22.3 70 48.3 70 73 7 114.3 1.6
2 50 165 25.4 84 60.3 73 92.1 7 127 1.6
2 1/2 65 190 28.6 100 73 79 104.8 7 149.2 1.6
3 80 210 31.8 117 88.9 83 127 7 168.3 1.6
3 1/2 90 230 35 133 101.6 86 139.7 7 184.2 1.6
4 100 275 38.1 152 114.3 102 157.2 7 215.9 1.6
5 125 330 44.5 189 141.3 114 185.7 7 266.7 1.6
6 150 355 47.7 222 168.3 117 215.9 7 292.1 1.6
8 200 420 55.6 273 219.1 133 269.9 7 349.2 1.6
10 250 510 63.5 343 273 152 323.8 7 431.8 1.6
12 300 560 66.7 400 323.8 156 381 7 489 1.6
14 350 605 69.9 432 355.6 165 412.8 7 527 1.6
16 400 685 76.2 495 406.4 178 469.9 7 603.2 1.6
18 450 745 82.6 546 457 184 533.4 7 654 1.6
20 500 815 88.9 610 508 190 584.2 7 723.9 1.6
24 600 940 101.6 718 610 203 692.2 7 838.2 1.6

Class 600 Weld Neck Flange Stud & Bolt Dimensions

Size in Inch Size in mm No of Bolts Bolt Size UNC RF Stud Length Hole Size ISO Stud Size Weight in kg
1/2 15 4 1/2 75 5/8 M14 1.5
3/4 20 4 5/8 90 3/4 M16 1.8
1 25 4 5/8 90 3/4 M16 1.8
1 1/4 32 4 5/8 95 3/4 M16 2.7
1 1/2 40 4 3/4 110 7/8 M20 3.7
2 50 8 5/8 110 3/4 M16 5.5
2 1/2 65 8 3/4 120 7/8 M20 8.2
3 80 8 3/4 125 7/8 M20 10.5
3 1/2 90 8 7/8 140 1 M24 11.8
4 100 8 7/8 145 1 M24 19.1
5 125 8 1 165 1 1/8 M27 31
6 150 12 1 170 1 1/8 M27 36
8 200 12 1 1/8 190 1 1/4 M30 55
10 250 16 1 1/4 215 1 3/8 M33 86
12 300 20 1 1/4 220 1 3/8 M33 102
14 350 20 1 3/8 235 1 1/2 M36 127
16 400 20 1 1/2 255 1 5/8 M39 177
18 450 20 1 5/8 275 1 3/4 M42 216
20 500 24 1 5/8 285 1 3/4 M42 268
24 600 24 1 7/8 330 2 M48 377

Class 900 Weld Neck Flange Dimensions

Size in Inch Size in mm Outer Diameter Flange Thickness Hub OD Weld Neck OD Welding Neck Length Bore RF Diameter RF Height PCD Weld Face
A B C D E F G H I J
1/2 15 120 22.3 38 21.3 60 Welding Neck bore is derived from the pipe schedule 34.9 7 82.6 1.6
3/4 20 130 25.4 44 26.7 70 42.9 7 88.9 1.6
1 25 150 28.6 52 33.4 73 50.8 7 101.6 1.6
1 1/4 32 160 28.6 64 42.2 73 63.5 7 111.1 1.6
1 1/2 40 180 31.8 70 48.3 83 73 7 123.8 1.6
2 50 215 38.1 105 60.3 102 92.1 7 165.1 1.6
2 1/2 65 245 41.3 124 73 105 104.8 7 190.5 1.6
3 80 240 38.1 127 88.9 102 127 7 190.5 1.6
4 100 290 44.5 159 114.3 114 157.2 7 235 1.6
5 125 350 50.8 190 141.3 127 185.7 7 279.4 1.6
6 150 380 55.6 235 168.3 140 215.9 7 317.5 1.6
8 200 470 63.5 298 219.1 162 269.9 7 393.7 1.6
10 250 545 69.9 368 273 184 323.8 7 469.9 1.6
12 300 610 79.4 419 323.8 200 381 7 533.4 1.6
14 350 640 85.8 451 355.6 213 412.8 7 558.8 1.6
16 400 705 88.9 508 406.4 216 469.9 7 616 1.6
18 450 785 101.6 565 457 229 533.4 7 685.8 1.6
20 500 855 108 622 508 248 584.2 7 749.3 1.6
24 600 1040 139.7 749 610 292 692.2 7 901.7 1.6

Class 900 Weld Neck Flange Stud & Bolt Dimensions

Size in Inch Size in mm No of Bolts Bolt Size UNC RF Stud Length Hole Size ISO Stud Size Weight in kg
1/2 15 4 3/4 110 7/8 M20 2.3
3/4 20 4 3/4 115 7/8 M20 2.7
1 25 4 7/8 125 1 M24 4.1
1 1/4 32 4 7/8 125 1 M24 4.6
1 1/2 40 4 1 140 1 1/8 M27 5.9
2 50 8 7/8 145 1 M24 11.5
2 1/2 65 8 1 160 1 1/8 M27 16.5
3 80 8 7/8 145 1 M24 14
4 100 8 1 1/8 170 1 1/4 M30 23
5 125 8 1 1/4 190 1 3/8 M33 39.5
6 150 12 1 1/8 190 1 1/4 M30 50
8 200 12 1 3/8 220 1 1/2 M36 80
10 250 16 1 3/8 235 1 1/2 M36 118
12 300 20 1 3/8 255 1 1/2 M36 148
14 350 20 1 1/2 275 1 5/8 M39 182
16 400 20 1 5/8 285 1 3/4 M42 225
18 450 20 1 7/8 325 2 M48 300
20 500 20 2 350 2 1/8 M52 373
24 600 20 2 1/2 440 2 5/8 M64 680

Class 1500 Weld Neck Flange Dimensions

Size in Inch Size in mm Outer Diameter Flange Thickness Hub OD Weld Neck OD Welding Neck Length Bore RF Diameter RF Height PCD Weld Face
A B C D E F G H I J
1/2 15 120 22.3 38 21.3 60 Welding Neck bore is derived from the pipe schedule 34.9 7 82.6 1.6
3/4 20 130 25.4 44 26.7 70 42.9 7 88.9 1.6
1 25 150 28.6 52 33.4 73 50.8 7 101.6 1.6
1 1/4 32 160 28.6 64 42.2 73 63.5 7 111.1 1.6
1 1/2 40 180 31.8 70 48.3 83 73 7 123.8 1.6
2 50 215 38.1 105 60.3 102 92.1 7 165.1 1.6
2 1/2 65 245 41.3 124 73 105 104.8 7 190.5 1.6
3 80 265 47.7 133 88.9 117 127 7 203.2 1.6
4 100 310 54 162 114.3 124 157.2 7 241.3 1.6
5 125 375 73.1 197 141.3 156 185.7 7 292.1 1.6
6 150 395 82.6 229 168.3 171 215.9 7 317.5 1.6
8 200 485 92.1 292 219.1 213 269.9 7 393.7 1.6
10 250 585 108 368 273 254 323.8 7 482.6 1.6
12 300 675 123.9 451 323.8 283 381 7 571.5 1.6
14 350 750 133.4 495 355.6 298 412.8 7 635 1.6
16 400 825 146.1 552 406.4 311 469.9 7 704.8 1.6
18 450 915 162 597 457 327 533.4 7 774.7 1.6
20 500 985 177.8 641 508 356 584.2 7 831.8 1.6
24 600 1170 203.2 762 610 406 692.2 7 990.6 1.6

Class 1500 Weld Neck Flange Stud & Bolt Dimensions

Size in Inch Size in mm No of Bolts Bolt Size UNC RF Stud Length Hole Size ISO Stud Size Weight in kg
1/2 15 4 3/4 110 7/8 M20 2.3
3/4 20 4 3/4 115 7/8 M20 2.7
1 25 4 7/8 125 1 M24 4.1
1 1/4 32 4 7/8 125 1 M24 4.6
1 1/2 40 4 1 140 1 1/8 M27 5.9
2 50 8 7/8 145 1 M24 11.4
2 1/2 65 8 1 160 1 1/8 M27 16.4
3 80 8 1 1/8 180 1 1/4 M30 21.8
4 100 8 1 1/4 195 1 3/8 M33 33
5 125 8 1 1/2 250 1 5/8 M39 59
6 150 12 1 3/8 260 1 1/2 M36 75
8 200 12 1 5/8 290 1 3/4 M42 125
10 250 12 1 7/8 335 2 M48 207
12 300 16 2 375 2 1/8 M52 314
14 350 16 2 1/4 405 2 3/8 M56 427
16 400 16 2 1/2 445 2 5/8 M64 568
18 450 16 2 3/4 495 2 7/8 M72 738
20 500 16 3 540 3 1/8 M76 932
24 600 16 3 1/2 615 3 5/8 M90 1511

Class 2500 Weld Neck Flange Dimensions

Size in Inch Size in mm Outer Diameter Flange Thickness Hub OD Weld Neck OD Welding Neck Length Bore RF Diameter RF Height PCD Weld Face
A B C D E F G H I J
1/2 15 135 30.2 43 21.3 73 Welding Neck bore is derived from the pipe schedule 34.9 7 88.9 1.6
3/4 20 140 31.8 51 26.7 79 42.9 7 95.2 1.6
1 25 160 35 57 33.4 89 50.8 7 108 1.6
1 1/4 32 185 38.1 73 42.2 95 63.5 7 130.2 1.6
1 1/2 40 205 44.5 79 48.3 111 73 7 146 1.6
2 50 235 50.9 95 60.3 127 92.1 7 171.4 1.6
2 1/2 65 265 57.2 114 73 143 104.8 7 196.8 1.6
3 80 305 66.7 133 88.9 168 127 7 228.6 1.6
4 100 355 76.2 165 114.3 190 157.2 7 273 1.6
5 125 420 92.1 203 141.3 229 185.7 7 323.8 1.6
6 150 485 108 235 168.3 273 215.9 7 368.3 1.6
8 200 550 127 305 219.1 318 269.9 7 438.2 1.6
10 250 675 165.1 375 273 419 323.8 7 539.8 1.6
12 300 760 184.2 441 323.8 464 381 7 619.1 1.6

Class 2500 Weld Neck Flange Stud & Bolt Dimensions

Size in Inch Size in mm No of Bolts Bolt Size UNC RF Stud Length Hole Size ISO Stud Size Weight in kg
1/2 15 4 3/4 120 7/8 M20 3.3
3/4 20 4 3/4 125 7/8 M20 3.7
1 25 4 7/8 140 1 M24 5.5
1 1/4 32 4 1 150 1 1/8 M27 7.8
1 1/2 40 4 1 1/8 170 1 1/4 M30 11.5
2 50 8 1 180 1 1/8 M27 19
2 1/2 65 8 1 1/8 195 1 1/4 M30 24
3 80 8 1 1/4 220 1 3/8 M33 42.8
4 100 8 1 1/2 255 1 5/8 M39 66
5 125 8 1 3/4 300 1 7/8 M45 111
6 150 8 2 345 2 1/8 M52 173
8 200 12 2 380 2 1/8 M52 264
10 250 12 2 1/2 490 2 5/8 M64 490
12 300 12 2 3/4 540 2 7/8 M72 695

Disclaimer –  Please check with ASME B16.5 Before using.