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ASME ANSI Flange Sizes

Nominal Pipe Size NPS (inches) Class 150
Diameter of Flange (inches) No. of Bolts Diameter of Bolts (inches) Bolt Circle (inches)
1/4 3-3/8 4 1/2 2-1/4
1/2 3-1/2 4 1/2 2-3/8
3/4 3-7/8 4 1/2 2-3/4
1 4-1/4 4 1/2 3-1/8
1-1/4 4-5/8 4 1/2 3-1/2
1-1/2 5 4 1/2 3-7/8
2 6 4 5/8 4-3/4
2-1/2 7 4 5/8 5-1/2
3 7-1/2 4 5/8 6
3-1/2 8-1/2 8 5/8 7
4 9 8 5/8 7-1/2
5 10 8 3/4 8-1/2
6 11 8 3/4 9-1/2
8 13-1/2 8 3/4 11-3/4
10 16 12 7/8 14-1/4
12 19 12 7/8 17
14 21 12 1 18-3/4
16 23-1/2 16 1 21-1/4
18 25 16 1-1/8 22-3/4
20 27-1/2 20 1-1/8 25
24 32 20 1-1/4 29-1/2
Nominal Pipe Size NPS (inches) Class 300
Diameter of Flange (inches) No. of Bolts Diameter of Bolts (inches) Bolt Circle (inches)
1/4 3-3/8 4 1/2 2-1/4
1/2 3-3/4 4 1/2 2-5/8
3/4 4-5/8 4 5/8 3-1/4
1 4-7/8 4 5/8 3-1/2
1-1/4 5-1/4 4 5/8 3-7/8
1-1/2 6-1/8 4 3/4 4-1/2
2 6-1/2 8 5/8 5
2-1/2 7-1/2 8 3/4 5-7/8
3 8-1/4 8 3/4 6-5/8
3-1/2 9 8 3/4 7-1/4
4 10 8 3/4 7-7/8
5 11 8 3/4 9-1/4
6 12-1/2 12 3/4 10-5/8
8 15 12 7/8 13
10 17-1/2 16 1 15-1/4
12 20-1/2 16 1-1/8 17-3/4
14 23 20 1-1/8 20-1/4
16 25-1/2 20 1-1/4 22-1/2
18 28 24 1-1/4 24-3/4
20 30-1/2 24 1-1/4 27
24 36 24 1-1/2 32
Nominal Pipe Size NPS (inches) Class 400
Diameter of Flange (inches) No. of Bolts Diameter of Bolts (inches) Bolt Circle (inches)
1/4 3-3/8 4 1/2 2-1/4
1/2 3-3/4 4 1/2 2-5/8
3/4 4-5/8 4 5/8 3-1/4
1 4-7/8 4 5/8 3-1/2
1-1/4 5-1/4 4 5/8 3-7/8
1-1/2 6-1/8 4 3/4 4-1/2
2 6-1/2 8 5/8 5
2-1/2 7-1/2 8 3/4 5-7/8
3 8-1/4 8 3/4 6-5/8
3-1/2 9 8 7/8 7-1/4
4 10 8 7/8 7-7/8
5 11 8 7/8 9-1/4
6 12-1/2 12 7/8 10-5/8
8 15 12 1 13
10 17-1/2 16 1-1/8 15-1/4
12 20-1/2 16 1-1/4 17-3/4
14 23 20 1-1/4 20-1/4
16 25-1/2 20 1-3/8 22-1/2
18 28 24 1-3/8 24-3/4
20 30-1/2 24 1-1/2 27
24 36 24 1-3/4 32
Nominal Pipe Size NPS (inches) Class 600
Diameter of Flange (inches) No. of Bolts Diameter of Bolts (inches) Bolt Circle (inches)
1/4 3-3/8 4 1/2 2-1/4
1/2 3-3/4 4 1/2 2-5/8
3/4 4-5/8 4 5/8 3-1/4
1 4-7/8 4 5/8 3-1/2
1-1/4 5-1/4 4 5/8 3-7/8
1-1/2 6-1/8 4 3/4 4-1/2
2 6-1/2 8 5/8 5
2-1/2 7-1/2 8 3/4 5-7/8
3 8-1/4 8 3/4 6-5/8
3-1/2 9 8 7/8 7-1/4
4 10-3/4 8 7/8 8-1/2
5 13 8 1 10-1/2
6 14 12 1 11-1/2
8 16-1/2 12 1-1/8 13-3/4
10 20 16 1-1/4 17
12 22 20 1-1/4 19-1/4
14 23-3/4 20 1-3/8 20-3/4
16 27 20 1-1/2 23-3/4
18 29-1/4 20 1-5/8 25-3/4
20 32 24 1-5/8 28-1/2
24 37 24 1-7/8 33
Nominal Pipe Size NPS (inches) Class 900
Diameter of Flange (inches) No. of Bolts Diameter of Bolts (inches) Bolt Circle (inches)
1/2 4-3/4 4 3/4 3-1/4
3/4 5-1/8 4 3/4 3-1/2
1 5-7/8 4 7/8 4
1-1/4 6-1/4 4 7/8 4-3/8
1-1/2 7 4 1 4-7/8
2 8-1/2 8 7/8 6-1/2
2-1/2 9-5/8 8 1 7-1/2
3 9-1/2 8 7/8 7-1/2
4 11-1/2 8 1-1/8 9-1/4
5 13-3/4 8 1-1/4 11
6 15 12 1-1/8 12-1/2
8 18-1/2 12 1-3/8 15-1/2
10 21-1/2 16 1-3/8 18-1/2
12 24 20 1-3/8 21
14 25-1/4 20 1-1/2 22
16 27-3/4 20 1-5/8 24-1/2
18 31 20 1-7/8 27
20 33-3/4 20 2 29-1/2
24 41 20 2-1/2 35-1/2
Nominal Pipe Size NPS (inches) Class 1500
Diameter of Flange (inches) No. of Bolts Diameter of Bolts (inches) Bolt Circle (inches)
1/2 4-3/4 4 3/4 3-1/4
3/4 5-1/8 4 3/4 3-1/2
1 5-7/8 4 7/8 4
1-1/4 6-1/4 4 7/8 4-3/8
1-1/2 7 4 1 4-7/8
2 8-1/2 8 7/8 6-1/2
2-1/2 9-5/8 8 1 7-1/2
3 10-1/2 8 1-1/8 8
4 12-1/4 8 1-1/4 9-1/2
5 14-3/4 8 1-1/2 11-1/2
6 15-1/2 12 1-3/8 12-1/2
8 19 12 1-5/8 15-1/2
10 23 12 1-7/8 19
12 26-1/2 16 2 22-1/2
14 29-1/2 16 2-1/4 25
16 32-1/2 16 2-1/2 27-3/4
18 36 16 2-3/4 30-1/2
20 38-3/4 16 3 32-3/4
24 46 16 3-1/2 39
Nominal Pipe Size NPS (inches) Class 2500
Diameter of Flange (inches) No. of Bolts Diameter of Bolts (inches) Bolt Circle (inches)
1/2 5-1/4 4 3/4 3-1/2
3/4 5-1/2 4 3/4 3-3/4
1 6-1/4 4 7/8 4-1/4
1-1/4 7-1/4 4 1 5-1/8
1-1/2 8 4 1-1/8 5-3/4
2 9-1/4 8 1 6-3/4
2-1/2 10-1/2 8 1-1/8 7-3/4
3 12 8 1-1/4 9
4 14 8 1-1/2 10-3/4
5 16-1/2 8 1-3/4 12-3/4
6 19 8 2 14-1/2
8 21-3/4 12 2 17-1/4
10 26-1/2 12 2-1/2 21-1/4
12 30 12 2-3/4 24-3/8