{
 "version": "2026-10-20",
 "license": "Dimension sheets: CC BY 4.0. Standard and published-size files: CC BY 4.0. Xem Studio's own designs (files_license = Xem Studio Design License): free to use and sell things from, not to redistribute as files — https://xemstudio.com/license/. Other publishers' files: their own license, linked beside them.",
 "slug": "asme-b16-5-flange-bolt-patterns",
 "name": "ASME B16.5 flange bolt patterns: bolt circle, number of holes and bolt size, Class 150 and 300, NPS ½ to 24",
 "kind": "standard",
 "category": "Tri-clamp & pipe",
 "group": "Pipe, tube & threads",
 "year": null,
 "question": "What is the bolt pattern of an ASME B16.5 flange (bolt circle, number of holes, bolt size) by NPS and class?",
 "tags": [
  "pipe",
  "flange",
  "b16.5",
  "bolt pattern",
  "bolt circle",
  "stud bolt",
  "standard"
 ],
 "aliases": [
  "150# flange bolt pattern",
  "2 inch 150# flange bolt pattern",
  "b16.5 bolt chart",
  "ansi flange bolt pattern",
  "flange bolt chart",
  "flange bolt circle",
  "flange bolt size chart",
  "300# flange bolt pattern",
  "class 150 bolt pattern",
  "class 300 bolt pattern",
  "flange stud bolt length",
  "flange bolt hole size",
  "how many bolts on a 4 inch flange",
  "pipe flange pcd"
 ],
 "overall_mm": {
  "length": null,
  "width": null,
  "height": null
 },
 "official_cad": false,
 "xem_status": "not-scanned",
 "les": false,
 "free_files": 0,
 "url": "https://xemstudio.com/objects/asme-b16-5-flange-bolt-patterns/",
 "sheet_txt": "https://xemstudio.com/objects/asme-b16-5-flange-bolt-patterns/sheet.txt",
 "sheet": {
  "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",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "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."
  ],
  "table": {
   "columns": [
    "class",
    "NPS",
    "holes",
    "bolt dia, in",
    "hole dia, in",
    "bolt circle, in (mm)",
    "stud length RF, in"
   ],
   "rows": [
    [
     "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"
    ]
   ]
  }
 },
 "sheet_text": "ASME B16.5 flange bolt patterns: bolt circle, number of holes and bolt size, Class 150 and 300, NPS ½ to 24 — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/asme-b16-5-flange-bolt-patterns/  (sheet CC BY 4.0)\nBasis: 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\nCatalog version: 2026-10-20\n\nSizes: see table below\n- 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.\n- 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.\n- Bolt holes straddle the centrelines; there is no hole on the vertical axis (the usual B16.5 layout, not stated in the tables cited).\n- 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).\n- Class 600 and above, and NPS 22, are not listed: no clean multi-source table was available.\n\nclass  NPS  holes  bolt dia, in  hole dia, in  bolt circle, in (mm)  stud length RF, in\n150  1/2  4  0.5  0.625  2.375 (60.3)  2.25\n150  3/4  4  0.5  0.625  2.750 (69.8)  2.5\n150  1  4  0.5  0.625  3.125 (79.4)  2.5\n150  1-1/4  4  0.5  0.625  3.500 (88.9)  2.75\n150  1-1/2  4  0.5  0.625  3.875 (98.4)  2.75\n150  2  4  0.625  0.75  4.750 (120.6)  3.25\n150  2-1/2  4  0.625  0.75  5.500 (139.7)  3.5\n150  3  4  0.625  0.75  6.000 (152.4)  3.5\n150  3-1/2  8  0.625  0.75  7.000 (177.8)  3.5\n150  4  8  0.625  0.75  7.500 (190.5)  3.5\n150  5  8  0.75  0.875  8.500 (215.9)  3.75\n150  6  8  0.75  0.875  9.500 (241.3)  4\n150  8  8  0.75  0.875  11.750 (298.4)  4.25\n150  10  12  0.875  1  14.250 (361.9)  4.5\n150  12  12  0.875  1  17.000 (431.8)  4.75\n150  14  12  1  1.125  18.750 (476.2)  5.25\n150  16  16  1  1.125  21.250 (539.8)  5.25\n150  18  16  1.125  1.25  22.750 (577.9)  5.75\n150  20  20  1.125  1.25  25.000 (635.0)  6.25\n150  24  20  1.25  1.375  29.500 (749.3)  6.75\n300  1/2  4  0.5  0.625  2.625 (66.7)  2.5\n300  3/4  4  0.625  0.75  3.250 (82.5)  3\n300  1  4  0.625  0.75  3.500 (88.9)  3\n300  1-1/4  4  0.625  0.75  3.875 (98.4)  3.25\n300  1-1/2  4  0.75  0.875  4.500 (114.3)  3.5\n300  2  8  0.625  0.75  5.000 (127.0)  3.5\n300  2-1/2  8  0.75  0.875  5.875 (149.2)  4\n300  3  8  0.75  0.875  6.625 (168.3)  4.25\n300  3-1/2  8  0.75  0.875  7.250 (184.1)  4.25\n300  4  8  0.75  0.875  7.875 (200.0)  4.5\n300  5  8  0.75  0.875  9.250 (234.9)  4.75\n300  6  12  0.75  0.875  10.625 (269.9)  4.75\n300  8  12  0.875  1  13.000 (330.2)  5.5\n300  10  16  1  1.125  15.250 (387.3)  6.25\n300  12  16  1.125  1.25  17.750 (450.8)  6.75\n300  14  20  1.125  1.25  20.250 (514.4)  7\n300  16  20  1.25  1.375  22.500 (571.5)  7.5\n300  18  24  1.25  1.375  24.750 (628.6)  7.75\n300  20  24  1.25  1.375  27.000 (685.8)  8\n300  24  24  1.5  1.625  32.000 (812.8)  9\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- 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/\n- 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/\n- 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\n- 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\n- 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/\n\nNo true-size file yet: the published figures do not fix the whole shape; a measured scan is planned.\nAPI: https://xemstudio.com/api/geometry?object=asme-b16-5-flange-bolt-patterns\n",
 "sources": [
  {
   "publisher": "Texas Flange",
   "title": "ANSI B16.5 Class 150 forged flange dimensions (inch)",
   "url": "https://texasflange.com/products/flange-dims-weights/ansi-b16-5-forged-flanges/class-150/",
   "formats": [
    "web"
   ],
   "license": "Publisher's page; dimensions are facts",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Texas Flange",
   "title": "ANSI B16.5 Class 300 forged flange dimensions (inch)",
   "url": "https://www.texasflange.com/products/flange-dims-weights/ansi-b16-5-forged-flanges/class-300/",
   "formats": [
    "web"
   ],
   "license": "Publisher's page; dimensions are facts",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Wermac",
   "title": "Weld neck flanges ASME B16.5 Class 150 (inch) with stud bolt table",
   "url": "https://wermac.org/flanges/dimensions_weldneck_in_asme-b16-5.html",
   "formats": [
    "web"
   ],
   "license": "Publisher's page; dimensions are facts",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Wermac",
   "title": "Stud bolts for ASME B16.5 Class 300 flanges (inch)",
   "url": "https://www.wermac.org/bolts/dimensions_stud-bolts_class-300_inches.html",
   "formats": [
    "web"
   ],
   "license": "Publisher's page; dimensions are facts",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Project Materials",
   "title": "Slip-on flange dimensions ASME B16.5 Class 150 and 300 (mm)",
   "url": "https://blog.projectmaterials.com/flanges/slip-on-flange-dimensions-asme-ansi/",
   "formats": [
    "web"
   ],
   "license": "Publisher's page; dimensions are facts",
   "license_verified": true,
   "hosted": false
  }
 ],
 "xem": {
  "status": "not-scanned",
  "sheet_free": true,
  "mesh_price_usd": null,
  "step_price_usd": null,
  "tolerance_mm": null
 },
 "related": [
  "asme-b16-5-class-150-flanges",
  "asme-b16-5-class-300-flanges",
  "butt-weld-elbows-long-radius",
  "butt-weld-equal-tees",
  "butt-weld-reducers",
  "schedule-40-pipe",
  "npt-thread-envelopes"
 ],
 "fits": [],
 "dimensions": "exact (nominal, no printing tolerance)",
 "dimension_rule": "All geometry on Xem Studio is exact (nominal, true size) with no printing tolerance. Where a part meets another part, the object lists its mating features (feature, exact size, what it mates with, fit class: press, slide, run, socket, clamp or designed). Apply your process's allowance to those features only; 'designed' gaps are part of the design and stay as drawn.",
 "mating": [],
 "faq": [
  {
   "q": "What is the bolt pattern of a 2 inch 150# flange?",
   "a": "4 holes of 0.75 in on a 4.750 in (120.6 mm) bolt circle, for 0.625 in bolts."
  },
  {
   "q": "What is the bolt pattern of a 6 inch 300# flange?",
   "a": "12 holes of 0.875 in on a 10.625 in (269.9 mm) bolt circle, for 0.75 in bolts."
  },
  {
   "q": "How many bolts does a 4 inch 150# flange have?",
   "a": "8 bolts of 5/8 in on a 7.5 in bolt circle."
  },
  {
   "q": "How do the 150# and 300# bolt patterns differ?",
   "a": "300# flanges use a larger bolt circle, usually larger bolts and, from NPS 2 up, more holes at the same size."
  }
 ],
 "files_license": null,
 "offers": [],
 "markdown": "https://xemstudio.com/objects/asme-b16-5-flange-bolt-patterns/index.md"
}