ASME B16.5 flange bolt patterns: bolt circle, number of holes and bolt size, Class 150 and 300, NPS ½ to 24 — dimension sheet Source: Xem Studio, https://xemstudio.com/objects/asme-b16-5-flange-bolt-patterns/ (sheet CC BY 4.0) Basis: ASME B16.5 bolt circle and hole counts from Texas Flange (inch) checked against Project Materials (mm); bolt diameter and stud length from Wermac's stud tables Catalog version: 2026-10-20 Sizes: see table below - Bolt circle, hole count and bolt size are the same for weld-neck, slip-on, blind, lap-joint, socket-weld and threaded flanges of one NPS and class. - Hole diameter is the bolt diameter plus 1/8 in. Stud length is for a raised-face joint (two flanges with 1/16 in raised faces, a gasket, two nuts) as printed in Wermac's tables; ring-joint studs are longer and are not listed. - Bolt holes straddle the centrelines; there is no hole on the vertical axis (the usual B16.5 layout, not stated in the tables cited). - Bolt circle is printed in inch; mm is the inch value × 25.4. Class 150 and Class 300 flange files with these holes are on the class pages (blind and slip-on flanges at every NPS). - Class 600 and above, and NPS 22, are not listed: no clean multi-source table was available. class NPS holes bolt dia, in hole dia, in bolt circle, in (mm) stud length RF, in 150 1/2 4 0.5 0.625 2.375 (60.3) 2.25 150 3/4 4 0.5 0.625 2.750 (69.8) 2.5 150 1 4 0.5 0.625 3.125 (79.4) 2.5 150 1-1/4 4 0.5 0.625 3.500 (88.9) 2.75 150 1-1/2 4 0.5 0.625 3.875 (98.4) 2.75 150 2 4 0.625 0.75 4.750 (120.6) 3.25 150 2-1/2 4 0.625 0.75 5.500 (139.7) 3.5 150 3 4 0.625 0.75 6.000 (152.4) 3.5 150 3-1/2 8 0.625 0.75 7.000 (177.8) 3.5 150 4 8 0.625 0.75 7.500 (190.5) 3.5 150 5 8 0.75 0.875 8.500 (215.9) 3.75 150 6 8 0.75 0.875 9.500 (241.3) 4 150 8 8 0.75 0.875 11.750 (298.4) 4.25 150 10 12 0.875 1 14.250 (361.9) 4.5 150 12 12 0.875 1 17.000 (431.8) 4.75 150 14 12 1 1.125 18.750 (476.2) 5.25 150 16 16 1 1.125 21.250 (539.8) 5.25 150 18 16 1.125 1.25 22.750 (577.9) 5.75 150 20 20 1.125 1.25 25.000 (635.0) 6.25 150 24 20 1.25 1.375 29.500 (749.3) 6.75 300 1/2 4 0.5 0.625 2.625 (66.7) 2.5 300 3/4 4 0.625 0.75 3.250 (82.5) 3 300 1 4 0.625 0.75 3.500 (88.9) 3 300 1-1/4 4 0.625 0.75 3.875 (98.4) 3.25 300 1-1/2 4 0.75 0.875 4.500 (114.3) 3.5 300 2 8 0.625 0.75 5.000 (127.0) 3.5 300 2-1/2 8 0.75 0.875 5.875 (149.2) 4 300 3 8 0.75 0.875 6.625 (168.3) 4.25 300 3-1/2 8 0.75 0.875 7.250 (184.1) 4.25 300 4 8 0.75 0.875 7.875 (200.0) 4.5 300 5 8 0.75 0.875 9.250 (234.9) 4.75 300 6 12 0.75 0.875 10.625 (269.9) 4.75 300 8 12 0.875 1 13.000 (330.2) 5.5 300 10 16 1 1.125 15.250 (387.3) 6.25 300 12 16 1.125 1.25 17.750 (450.8) 6.75 300 14 20 1.125 1.25 20.250 (514.4) 7 300 16 20 1.25 1.375 22.500 (571.5) 7.5 300 18 24 1.25 1.375 24.750 (628.6) 7.75 300 20 24 1.25 1.375 27.000 (685.8) 8 300 24 24 1.5 1.625 32.000 (812.8) 9 Files elsewhere (not hosted by Xem Studio; license as stated by the publisher): - Texas Flange: ANSI B16.5 Class 150 forged flange dimensions (inch) — web — Publisher's page; dimensions are facts — https://texasflange.com/products/flange-dims-weights/ansi-b16-5-forged-flanges/class-150/ - Texas Flange: ANSI B16.5 Class 300 forged flange dimensions (inch) — web — Publisher's page; dimensions are facts — https://www.texasflange.com/products/flange-dims-weights/ansi-b16-5-forged-flanges/class-300/ - Wermac: Weld neck flanges ASME B16.5 Class 150 (inch) with stud bolt table — web — Publisher's page; dimensions are facts — https://wermac.org/flanges/dimensions_weldneck_in_asme-b16-5.html - Wermac: Stud bolts for ASME B16.5 Class 300 flanges (inch) — web — Publisher's page; dimensions are facts — https://www.wermac.org/bolts/dimensions_stud-bolts_class-300_inches.html - Project Materials: Slip-on flange dimensions ASME B16.5 Class 150 and 300 (mm) — web — Publisher's page; dimensions are facts — https://blog.projectmaterials.com/flanges/slip-on-flange-dimensions-asme-ansi/ No true-size file yet: the published figures do not fix the whole shape; a measured scan is planned. API: https://xemstudio.com/api/geometry?object=asme-b16-5-flange-bolt-patterns