Flanges and Bolt Dimensions – Class 150 to 2500 ASME/ANSI B16.5

Diameters and bolt circles for standard ASME B16.5 flanges – 1/4 to 24 inches – Class 150 to 2500

Flange dimensions are determined by pipe size and pressure class required for the application. Most of these dimensions have been standardized and published as ASME, MSS, API or other standardization organization specifications. ASME/ANSI B16.5 provides dimensions and tolerances for flanges in pipe sizes from 1/2″ through 24″ and in classes ranging 150 through 2500.

Class 150
Nominal Pipe Size
NPS
(inches)
Diameter of
Flange
(inches)
No.
of
Bolts
Diameter
of Bolts
(inches)
Bolt
Circle
(inches)
Length Mach.
Bolts
(inches)
Length Stud
Bolts
(inches)
1/4 3-3/8 4 1/2 2-1/4 2.00 2.50
1/2 3-1/2 4 1/2 2-3/8 2.00 2.50
3/4 3-7/8 4 1/2 2-3/4 2.25 2.50
1 4-1/4 4 1/2 3-1/8 2.25 2.75
1-1/4 4-5/8 4 1/2 3-1/2 2.50 2.75
1-1/2 5 4 1/2 3-7/8 2.50 3.00
2 6 4 5/8 4-3/4 2.75 3.35
2-1/2 7 4 5/8 5-1/2 3.00 3.50
3 7-1/2 4 5/8 6 3.25 3.75
3-1/2 8-1/2 8 5/8 7 3.25 3.75
4 9 8 5/8 7-1/2 3.25 3.75
5 10 8 3/4 8-1/2 3.25 4.00
6 11 8 3/4 9-1/2 3.50 4.00
8 13-1/2 8 3/4 11-3/4 3.75 4.25
10 16 12 7/8 14-1/4 4.25 4.75
12 19 12 7/8 17 4.25 4.75
14 21 12 1 18-3/4 4.50 5.25
16 23-1/2 16 1 21-1/4 4.75 5.50
18 25 16 1-1/8 22-3/4 5.00 6.00
20 27-1/2 20 1-1/8 25 5.50 6.25
24 32 20 1-1/4 29-1/2 6.00 7.00

 

Class 300
Nominal Pipe Size
NPS
(inches)
Diameter of
Flange
(inches)
No.
of
Bolts
Diameter
of Bolts
(inches)
Bolt
Circle
(inches)
Length Mach.
Bolts
(inches)
Length Stud
Bolts
(inches)
1/4 3-3/8 4 1/2 2-1/4 2.25 2.75
1/2 3-3/4 4 1/2 2-5/8 2.25 2.75
3/4 4-5/8 4 5/8 3-1/4 2.50 3.00
1 4-7/8 4 5/8 3-1/2 2.75 3.25
1-1/4 5-1/4 4 5/8 3-7/8 2.75 3.25
1-1/2 6-1/8 4 3/4 4-1/2 3.00 3.75
2 6-1/2 8 5/8 5 3.00 3.50
2-1/2 7-1/2 8 3/4 5-7/8 3.50 4.00
3 8-1/4 8 3/4 6-5/8 3.75 4.25
3-1/2 9 8 3/4 7-1/4 3.75 4.50
4 10 8 3/4 7-7/8 4.00 4.50
5 11 8 3/4 9-1/4 4.25 4.75
6 12-1/2 12 3/4 10-5/8 4.25 5.00
8 15 12 7/8 13 4.75 5.50
10 17-1/2 16 1 15-1/4 5.50 6.25
12 20-1/2 16 1-1/8 17-3/4 6.00 6.75
14 23 20 1-1/8 20-1/4 6.25 7.00
16 25-1/2 20 1-1/4 22-1/2 6.50 7.50
18 28 24 1-1/4 24-3/4 6.75 7.75
20 30-1/2 24 1-1/4 27 7.25 8.25
24 36 24 1-1/2 32 8.00 9.25

 

Class 400
Nominal Pipe Size
NPS
(inches)
Diameter of
Flange
(inches)
No.
of
Bolts
Diameter
of Bolts
(inches)
Bolt
Circle
(inches)
Length Mach.
Bolts
(inches)
Length Stud
Bolts
(inches)
1/4 3-3/8 4 1/2 2-1/4
1/2 3-3/4 4 1/2 2-5/8 3.00
3/4 4-5/8 4 5/8 3-1/4 3.50
1 4-7/8 4 5/8 3-1/2 3.50
1-1/4 5-1/4 4 5/8 3-7/8 3.75
1-1/2 6-1/8 4 3/4 4-1/2 4.25
2 6-1/2 8 5/8 5 4.25
2-1/2 7-1/2 8 3/4 5-7/8 4.75
3 8-1/4 8 3/4 6-5/8 5.00
3-1/2 9 8 7/8 7-1/4 5.50
4 10 8 7/8 7-7/8 5.50
5 11 8 7/8 9-1/4 5.75
6 12-1/2 12 7/8 10-5/8 6.00
8 15 12 1 13 6.75
10 17-1/2 16 1-1/8 15-1/4 7.50
12 20-1/2 16 1-1/4 17-3/4 8.00
14 23 20 1-1/4 20-1/4 8.25
16 25-1/2 20 1-3/8 22-1/2 8.75
18 28 24 1-3/8 24-3/4 9.00
20 30-1/2 24 1-1/2 27 9.50
24 36 24 1-3/4 32 10.50

 

Class 600
Nominal Pipe Size
NPS
(inches)
Diameter of
Flange
(inches)
No.
of
Bolts
Diameter
of Bolts
(inches)
Bolt
Circle
(inches)
Length Mach.
Bolts
(inches)
Length Stud
Bolts
(inches)
1/4 3-3/8 4 1/2 2-1/4
1/2 3-3/4 4 1/2 2-5/8 3.00
3/4 4-5/8 4 5/8 3-1/4 3.50
1 4-7/8 4 5/8 3-1/2 3.50
1-1/4 5-1/4 4 5/8 3-7/8 3.75
1-1/2 6-1/8 4 3/4 4-1/2 4.25
2 6-1/2 8 5/8 5 4.25
2-1/2 7-1/2 8 3/4 5-7/8 4.75
3 8-1/4 8 3/4 6-5/8 5.00
3-1/2 9 8 7/8 7-1/4 5.50
4 10-3/4 8 7/8 8-1/2 5.75
5 13 8 1 10-1/2 6.50
6 14 12 1 11-1/2 6.75
8 16-1/2 12 1-1/8 13-3/4 7.50
10 20 16 1-1/4 17 8.50
12 22 20 1-1/4 19-1/4 8.75
14 23-3/4 20 1-3/8 20-3/4 9.25
16 27 20 1-1/2 23-3/4 10.00
18 29-1/4 20 1-5/8 25-3/4 10.75
20 32 24 1-5/8 28-1/2 11.25
24 37 24 1-7/8 33 13.00

 

Class 900
Nominal Pipe Size
NPS
(inches)
Diameter of
Flange
(inches)
No.
of
Bolts
Diameter
of Bolts
(inches)
Bolt
Circle
(inches)
Length Mach.
Bolts
(inches)
Length Stud
Bolts
(inches)
1/2 4-3/4 4 3/4 3-1/4 4.25
3/4 5-1/8 4 3/4 3-1/2 4.50
1 5-7/8 4 7/8 4 5.00
1-1/4 6-1/4 4 7/8 4-3/8 5.00
1-1/2 7 4 1 4-7/8 5.50
2 8-1/2 8 7/8 6-1/2 5.75
2-1/2 9-5/8 8 1 7-1/2 6.25
3 9-1/2 8 7/8 7-1/2 5.75
4 11-1/2 8 1-1/8 9-1/4 6.75
5 13-3/4 8 1-1/4 11 7.50
6 15 12 1-1/8 12-1/2 7.50
8 18-1/2 12 1-3/8 15-1/2 8.75
10 21-1/2 16 1-3/8 18-1/2 9.25
12 24 20 1-3/8 21 10.00
14 25-1/4 20 1-1/2 22 10.75
16 27-3/4 20 1-5/8 24-1/2 11.25
18 31 20 1-7/8 27 12.75
20 33-3/4 20 2 29-1/2 13.75
24 41 20 2-1/2 35-1/2 17.25

 

Class 1500
Nominal Pipe Size
NPS
(inches)
Diameter of
Flange
(inches)
No.
of
Bolts
Diameter
of Bolts
(inches)
Bolt
Circle
(inches)
Length Mach.
Bolts
(inches)
Length Stud
Bolts
(inches)
1/2 4-3/4 4 3/4 3-1/4 4.25
3/4 5-1/8 4 3/4 3-1/2 4.50
1 5-7/8 4 7/8 4 5.00
1-1/4 6-1/4 4 7/8 4-3/8 5.00
1-1/2 7 4 1 4-7/8 5.50
2 8-1/2 8 7/8 6-1/2 5.75
2-1/2 9-5/8 8 1 7-1/2 6.25
3 10-1/2 8 1-1/8 8 7.00
4 12-1/4 8 1-1/4 9-1/2 7.75
5 14-3/4 8 1-1/2 11-1/2 9.75
6 15-1/2 12 1-3/8 12-1/2 <10.25/td>
8 19 12 1-5/8 15-1/2 11.50
10 23 12 1-7/8 19 13.25
12 26-1/2 16 2 22-1/2 14.75
14 29-1/2 16 2-1/4 25 16.00
16 32-1/2 16 2-1/2 27-3/4 17.50
18 36 16 2-3/4 30-1/2 19.50
20 38-3/4 16 3 32-3/4 21.25
24 46 16 3-1/2 39 24.25

 

Class 2500
Nominal Pipe Size
NPS
(inches)
Diameter of
Flange
(inches)
No.
of
Bolts
Diameter
of Bolts
(inches)
Bolt
Circle
(inches)
Length Mach.
Bolts
(inches)
Length Stud
Bolts
(inches)
1/2 5-1/4 4 3/4 3-1/2 4.75
3/4 5-1/2 4 3/4 3-3/4 5.00
1 6-1/4 4 7/8 4-1/4 5.50
1-1/4 7-1/4 4 1 5-1/8 6.00
1-1/2 8 4 1-1/8 5-3/4 6.75
2 9-1/4 8 1 6-3/4 7.00
2-1/2 10-1/2 8 1-1/8 7-3/4 7.75
3 12 8 1-1/4 9 8.75
4 14 8 1-1/2 10-3/4 10.00
5 16-1/2 8 1-3/4 12-3/4 11.75
6 19 8 2 14-1/2 13.50
8 21-3/4 12 2 17-1/4 15.00
10 26-1/2 12 2-1/2 21-1/4 19.25
12 30 12 2-3/4 24-3/8 21.25