STANDARD · ASME-B16-5

ASME B16.5 Flange Dimensions

ASME B16.5-2025 · ASME B16.5

ASME B16.5-2025North America, Middle East, South-East Asiapressure class

ASME B16.5 is the baseline American flange standard for pipe sizes NPS 1/2 to NPS 24 in pressure classes 150 through 2500. It defines outside diameter, flange thickness, raised-face diameter and height, bolt circle, bolt count, bolt hole diameter and hub geometry for weld neck, slip-on, blind, socket-weld, threaded and lap-joint flanges.

Because B16.5 is organised by nominal pipe size and class, a flange is only interchangeable with another B16.5 flange of the same size, class and facing. Class sets the wall thickness, bolt count and bolt size; the actual allowable pressure is read from the B16.5 pressure–temperature tables for the material group and design temperature. Above NPS 24, ASME B16.47 takes over — the two standards are not interchangeable. Coverage limits are part of the standard: Class 2500 runs only to NPS 12 and has no slip-on flanges, Class 1500 slip-on flanges stop at NPS 2-1/2, and Classes 900, 1500 and 2500 have no NPS 3-1/2.

Base materialASTM A105

Size notationNPS (inch)

Material options5 groups

Reference data5 topics

DIMENSIONS

Dimension tables

One row per specification. Open a size for the drawing, pressure ratings and printable A4 sheet.

Weld Neck 136 Slip-On 110 Blind 136

Weld Neck: Butt-welded to the pipe with a tapered hub; used for high pressure, high temperature and cyclic service. 136 specifications.

136 specifications

Size	Rating	Outside Ø D	Thickness C	Raised face D2	Bolt circle K	Bolting	Hub A	Length H	Weight
1/2″DN15	Class 150	88.9	9.7	35.1	60.5	4 × Ø15.9	30.2	46	0.9 kg	Spec sheet
1/2″DN15	Class 300	95.3	12.7	35.1	66.5	4 × Ø15.9	38.1	50.8	0.9 kg	Spec sheet
1/2″DN15	Class 400	95.3	14.2	35.1	66.5	4 × Ø15.9	38.1	52.3	0.9 kg	Spec sheet
1/2″DN15	Class 600	95.3	14.2	35.1	66.5	4 × Ø15.9	38.1	52.3	0.9 kg	Spec sheet
1/2″DN15	Class 900	120.7	22.4	35.1	82.6	4 × Ø22.2	38.1	60.5	2.3 kg	Spec sheet
1/2″DN15	Class 1500	120.7	22.4	35.1	82.6	4 × Ø22.2	38.1	60.5	2.3 kg	Spec sheet
1/2″DN15	Class 2500	133.4	30.2	35.1	88.9	4 × Ø22.2	42.9	73.2	3.2 kg	Spec sheet
3/4″DN20	Class 150	98.6	11.2	42.9	69.9	4 × Ø15.9	38.1	50.8	0.9 kg	Spec sheet
3/4″DN20	Class 300	117.3	14.2	42.9	82.6	4 × Ø19.1	47.8	55.6	1.4 kg	Spec sheet
3/4″DN20	Class 400	117.3	15.7	42.9	82.6	4 × Ø19.1	47.8	57.2	1.8 kg	Spec sheet
3/4″DN20	Class 600	117.3	15.7	42.9	82.6	4 × Ø19.1	47.8	57.2	1.8 kg	Spec sheet
3/4″DN20	Class 900	130	25.4	42.9	88.9	4 × Ø22.2	44.5	69.9	2.7 kg	Spec sheet
3/4″DN20	Class 1500	130	25.4	42.9	88.9	4 × Ø22.2	44.5	69.9	2.7 kg	Spec sheet
3/4″DN20	Class 2500	139.7	31.8	42.9	95.3	4 × Ø22.2	50.8	79.2	3.6 kg	Spec sheet
1″DN25	Class 150	108	12.7	50.8	79.2	4 × Ø15.9	49.3	53.8	1.4 kg	Spec sheet
1″DN25	Class 300	124	15.7	50.8	88.9	4 × Ø19.1	53.8	60.5	1.8 kg	Spec sheet
1″DN25	Class 400	124	17.5	50.8	88.9	4 × Ø19.1	53.8	62	1.8 kg	Spec sheet
1″DN25	Class 600	124	17.5	50.8	88.9	4 × Ø19.1	53.8	62	1.8 kg	Spec sheet
1″DN25	Class 900	149.4	28.4	50.8	101.6	4 × Ø25.4	52.3	73.2	4.1 kg	Spec sheet
1″DN25	Class 1500	149.4	28.4	50.8	101.6	4 × Ø25.4	52.3	73.2	4.1 kg	Spec sheet
1″DN25	Class 2500	158.8	35.1	50.8	108	4 × Ø25.4	57.2	88.9	5.4 kg	Spec sheet
1¼″DN32	Class 150	117.3	14.2	63.5	88.9	4 × Ø15.9	58.7	55.6	1.4 kg	Spec sheet
1¼″DN32	Class 300	133.4	17.5	63.5	98.6	4 × Ø19.1	63.5	63.5	2.3 kg	Spec sheet
1¼″DN32	Class 400	133.4	20.6	63.5	98.6	4 × Ø19.1	63.5	66.5	2.7 kg	Spec sheet
1¼″DN32	Class 600	133.4	20.6	63.5	98.6	4 × Ø19.1	63.5	66.5	2.7 kg	Spec sheet
1¼″DN32	Class 900	158.8	28.4	63.5	111.3	4 × Ø25.4	63.5	73.2	4.5 kg	Spec sheet
1¼″DN32	Class 1500	158.8	28.4	63.5	111.3	4 × Ø25.4	63.5	73.2	4.5 kg	Spec sheet
1¼″DN32	Class 2500	184.2	38.1	63.5	130	4 × Ø28.6	73.2	95.3	7.7 kg	Spec sheet
1½″DN40	Class 150	127	15.7	73.2	98.6	4 × Ø15.9	65	60.5	1.8 kg	Spec sheet
1½″DN40	Class 300	155.4	19.1	73.2	114.3	4 × Ø22.2	69.9	66.8	3.2 kg	Spec sheet
1½″DN40	Class 400	155.4	22.4	73.2	114.3	4 × Ø22.2	69.9	69.9	3.6 kg	Spec sheet
1½″DN40	Class 600	155.4	22.4	73.2	114.3	4 × Ø22.2	69.9	69.9	3.6 kg	Spec sheet
1½″DN40	Class 900	177.8	31.8	73.2	124	4 × Ø28.6	69.9	82.6	5.9 kg	Spec sheet
1½″DN40	Class 1500	177.8	31.8	73.2	124	4 × Ø28.6	69.9	82.6	5.9 kg	Spec sheet
1½″DN40	Class 2500	203.2	44.5	73.2	146.1	4 × Ø31.8	79.2	111.3	11.3 kg	Spec sheet
2″DN50	Class 150	152.4	17.5	91.9	120.7	4 × Ø19.1	77.7	62	2.7 kg	Spec sheet
2″DN50	Class 300	165.1	20.6	91.9	127	8 × Ø19.1	84.1	68.3	4.1 kg	Spec sheet
2″DN50	Class 400	165.1	25.4	91.9	127	8 × Ø19.1	84.1	73.2	5.4 kg	Spec sheet
2″DN50	Class 600	165.1	25.4	91.9	127	8 × Ø19.1	84.1	73.2	5.4 kg	Spec sheet
2″DN50	Class 900	215.9	38.1	91.9	165.1	8 × Ø25.4	104.6	101.6	11.3 kg	Spec sheet
2″DN50	Class 1500	215.9	38.1	91.9	165.1	8 × Ø25.4	104.6	101.6	11.3 kg	Spec sheet
2″DN50	Class 2500	235	50.8	91.9	171.5	8 × Ø28.6	95.3	127	19.1 kg	Spec sheet
2½″DN65	Class 150	177.8	20.6	104.6	139.7	4 × Ø19.1	90.4	68.3	3.6 kg	Spec sheet
2½″DN65	Class 300	190.5	23.9	104.6	149.4	8 × Ø22.2	100.1	74.7	5.4 kg	Spec sheet
2½″DN65	Class 400	190.5	28.4	104.6	149.4	8 × Ø22.2	100.1	79.2	8.2 kg	Spec sheet
2½″DN65	Class 600	190.5	28.4	104.6	149.4	8 × Ø22.2	100.1	79.2	8.2 kg	Spec sheet
2½″DN65	Class 900	244.3	41.1	104.6	190.5	8 × Ø28.6	124	104.6	16.3 kg	Spec sheet
2½″DN65	Class 1500	244.3	41.1	104.6	190.5	8 × Ø28.6	124	104.6	16.3 kg	Spec sheet
2½″DN65	Class 2500	266.7	57.2	104.6	196.9	8 × Ø31.8	114.3	142.7	23.6 kg	Spec sheet
3″DN80	Class 150	190.5	22.4	127	152.4	4 × Ø19.1	108	68.3	4.5 kg	Spec sheet
3″DN80	Class 300	209.6	26.9	127	168.1	8 × Ø22.2	117.3	77.7	6.8 kg	Spec sheet
3″DN80	Class 400	209.6	31.8	127	168.1	8 × Ø22.2	117.3	82.6	10.4 kg	Spec sheet
3″DN80	Class 600	209.6	31.8	127	168.1	8 × Ø22.2	117.3	82.6	10.4 kg	Spec sheet
3″DN80	Class 900	241.3	38.1	127	190.5	8 × Ø25.4	127	101.6	14.1 kg	Spec sheet
3″DN80	Class 1500	266.7	47.8	127	203.2	8 × Ø31.8	133.4	117.3	21.8 kg	Spec sheet
3″DN80	Class 2500	304.8	66.5	127	228.6	8 × Ø34.9	133.4	168.1	42.6 kg	Spec sheet
3½″DN90	Class 150	215.9	22.4	139.7	177.8	8 × Ø19.1	122.2	69.9	5.4 kg	Spec sheet
3½″DN90	Class 300	228.6	28.4	139.7	184.2	8 × Ø22.2	133.4	79.5	8.2 kg	Spec sheet
3½″DN90	Class 400	228.6	35.1	139.7	184.2	8 × Ø25.4	133.4	85.9	11.8 kg	Spec sheet
3½″DN90	Class 600	228.6	35.1	139.7	184.2	8 × Ø25.4	133.4	85.9	11.8 kg	Spec sheet
4″DN100	Class 150	228.6	22.4	157.2	190.5	8 × Ø19.1	134.9	74.7	6.8 kg	Spec sheet
4″DN100	Class 300	254	30.2	157.2	200.2	8 × Ø22.2	146.1	84.3	11.3 kg	Spec sheet
4″DN100	Class 400	254	35.1	157.2	200.2	8 × Ø25.4	146.1	88.9	15.9 kg	Spec sheet
4″DN100	Class 600	273.1	38.1	157.2	215.9	8 × Ø25.4	152.4	101.6	19.1 kg	Spec sheet
4″DN100	Class 900	292.1	44.5	157.2	235	8 × Ø31.8	158.8	114.3	24 kg	Spec sheet
4″DN100	Class 1500	311.2	53.8	157.2	241.3	8 × Ø34.9	162.1	124	33.1 kg	Spec sheet
4″DN100	Class 2500	355.6	76.2	157.2	273.1	8 × Ø41.3	165.1	190.5	65.8 kg	Spec sheet
5″DN125	Class 150	254	22.4	185.7	215.9	8 × Ø22.2	163.6	87.4	8.6 kg	Spec sheet
5″DN125	Class 300	279.4	33.3	185.7	235	8 × Ø22.2	177.8	97	14.5 kg	Spec sheet
5″DN125	Class 400	279.4	38.1	185.7	235	8 × Ø25.4	177.8	101.6	19.5 kg	Spec sheet
5″DN125	Class 600	330.2	44.5	185.7	266.7	8 × Ø28.6	189	114.3	30.8 kg	Spec sheet
5″DN125	Class 900	349.3	50.8	185.7	279.4	8 × Ø34.9	190.5	127	39 kg	Spec sheet
5″DN125	Class 1500	374.7	73.2	185.7	292.1	8 × Ø41.3	196.9	155.4	59 kg	Spec sheet
5″DN125	Class 2500	419.1	91.9	185.7	323.9	8 × Ø47.6	203.2	228.6	111 kg	Spec sheet
6″DN150	Class 150	279.4	23.9	215.9	241.3	8 × Ø22.2	192	87.4	10.9 kg	Spec sheet
6″DN150	Class 300	317.5	35.1	215.9	269.7	12 × Ø22.2	206.2	97	19.1 kg	Spec sheet
6″DN150	Class 400	317.5	41.1	215.9	269.7	12 × Ø25.4	206.2	103.1	25.9 kg	Spec sheet
6″DN150	Class 600	355.6	47.8	215.9	292.1	12 × Ø28.6	222.3	117.3	36.7 kg	Spec sheet
6″DN150	Class 900	381	55.6	215.9	317.5	12 × Ø31.8	235	139.7	49.9 kg	Spec sheet
6″DN150	Class 1500	393.7	82.6	215.9	317.5	12 × Ø38.1	228.6	171.5	74.8 kg	Spec sheet

REFERENCE

Pressure ratings, materials and tolerances

Transcribed from ASME B16.5-2025 with table and page references.

Pressure-temperature ratings

ASME B16.5-2025 pressure ratings by material group

Tables 2-1.1 (SI units, bar) and 2-1.1C (U.S. Customary units, psig) of ASME B16.5-2025 give the maximum allo…

Open reference Material groups

ASME B16.5-2025 material groups and bolting tables

Table 1.1-1 is the master material list of ASME B16.5-2025. For every accepted material it gives four things:…

Open reference Tolerances

ASME B16.5-2025 flange tolerances (Section 7)

Section 7 of ASME B16.5-2025 sets the manufacturing and inspection tolerances for flanges and flanged fitting…

Open reference Marking

ASME B16.5-2025 marking requirements (Section 4)

Section 4 of ASME B16.5-2025 defines the identification markings that must be applied to flanges and flanged …

Open reference Edition changes

ASME B16.5-2025: what changed from the 2020 edition

ASME B16.5-2025 is the current edition of the American pipe-flange and flanged-fitting standard, covering NPS…

Open reference

How to read the pressure class

ASME classes are not fixed pressures. For ASTM A105 (material group 1.1) the ASME B16.5-2025 ambient rating is 285 psi (19.6 bar) at Class 150, 740 psi (51.0 bar) at Class 300, 985 psi (68.0 bar) at Class 400, 1,480 psi (102.0 bar) at Class 600, 2,220 psi (153.1 bar) at Class 900, 3,705 psi (255.1 bar) at Class 1500 and 6,170 psi (425.1 bar) at Class 2500 at 38 °C (100 °F), derating as temperature rises. The 2025 edition revised the rating tables (record 23-2509); these are the 2025 values and the full temperature tables are on the ASME B16.5 pressure-ratings page.

Edition and verification

Dimension values on this page have been checked cell by cell against ASME B16.5-2025, using both the SI and U.S. Customary tables. The 2025 edition revised the bore (B) dimension figures and the minimum hub-height method, neither of which is a field published in these tables; outside diameter, thickness, hub, length, bolt circle and bolt-hole values match the 2025 edition. Raised-face height follows the 2025 rule: 1.5 mm for Classes 150 and 300, 6.4 mm for Classes 400 to 2500.

Data imported 2026-11-05 08:05.