{
 "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": "picatinny-rail-mil-std-1913",
 "name": "Picatinny rail (MIL-STD-1913): profile, grooves and mount jaw",
 "kind": "standard",
 "category": "Hardware",
 "group": "Mounting standards",
 "year": null,
 "question": "What are the exact Picatinny rail dimensions (MIL-STD-1913)?",
 "tags": [
  "rail",
  "mount",
  "accessory mount",
  "picatinny",
  "airsoft",
  "scope mount",
  "light mount",
  "standard"
 ],
 "aliases": [
  "picatinny rail dimensions",
  "mil-std-1913",
  "1913 rail",
  "picatinny slot width",
  "picatinny slot spacing",
  "picatinny rail stl",
  "picatinny rail profile",
  "picatinny mount design",
  "20mm rail",
  "airsoft rail dimensions",
  "weaver vs picatinny"
 ],
 "overall_mm": {
  "length": null,
  "width": 21.209,
  "height": 9.322
 },
 "official_cad": false,
 "xem_status": "free-files",
 "les": false,
 "free_files": 6,
 "url": "https://xemstudio.com/objects/picatinny-rail-mil-std-1913/",
 "sheet_txt": "https://xemstudio.com/objects/picatinny-rail-mil-std-1913/sheet.txt",
 "sheet": {
  "basis": "MIL-STD-1913 (AR), Figures 1 and 2 (public release)",
  "overall_mm": {
   "length": null,
   "width": 21.209,
   "height": 9.322
  },
  "notes": [
   "MIL-STD-1913 is the Picatinny accessory rail: lights, lasers, optics, red dots, grips, bipods, cameras and phone mounts clamp across its 45° dovetail flanks, and a key in the clamp sits in a recoil groove so the accessory cannot slide.",
   "Every number here is from the standard's Figure 1 (profile) and Figure 2 (recoil groove), printed in inches; the mm values are exact conversions. The standard is public (Distribution Statement A).",
   "Groove dimensions apply to all grooves; the number of grooves depends on the application. Accessory makers often count rail length in slots: an n-slot section is n × .394 in long.",
   "The mount-jaw file is the female shape at nominal size with one recoil key: subtract or adapt it for your mount, and add your process clearance on the flanks (a printed clamp typically needs a few tenths of a mm).",
   "Weaver rails share the outer shape loosely but have narrower .180 in grooves without a fixed spacing: Weaver accessories usually fit Picatinny, Picatinny accessories often do not fit Weaver."
  ],
  "table": {
   "columns": [
    "parameter",
    "value"
   ],
   "rows": [
    [
     "width across the 45° edges",
     ".835 −.005 in (21.209 mm)"
    ],
    [
     "top flat (datum C)",
     ".748 ±.002 in (18.999 mm)"
    ],
    [
     "neck width",
     ".617 −.010 in (15.672 mm)"
    ],
    [
     "lower flank",
     "45°, .108 in (2.743 mm) deep (basic)"
    ],
    [
     "upper edge",
     "45° from the top flat to the widest point (1.105 mm)"
    ],
    [
     "top to neck",
     ".164 −.020 in"
    ],
    [
     "rail height above the mounting surface",
     ".367 in min (9.322 mm)"
    ],
    [
     "recoil groove width",
     ".206 +.008/−0 in (5.232 mm)"
    ],
    [
     "recoil groove depth",
     ".118 +.008/−0 in (2.997 mm)"
    ],
    [
     "groove spacing (centre to centre)",
     ".394 in basic (10.008 mm)"
    ],
    [
     "edge break / fillets",
     ".002 +.010 in / .020 ±.015 in"
    ]
   ]
  }
 },
 "sheet_text": "Picatinny rail (MIL-STD-1913): profile, grooves and mount jaw — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/picatinny-rail-mil-std-1913/  (sheet CC BY 4.0)\nBasis: MIL-STD-1913 (AR), Figures 1 and 2 (public release)\nCatalog version: 2026-10-20\n\nOverall (mm): width 21.209, height 9.322\n- MIL-STD-1913 is the Picatinny accessory rail: lights, lasers, optics, red dots, grips, bipods, cameras and phone mounts clamp across its 45° dovetail flanks, and a key in the clamp sits in a recoil groove so the accessory cannot slide.\n- Every number here is from the standard's Figure 1 (profile) and Figure 2 (recoil groove), printed in inches; the mm values are exact conversions. The standard is public (Distribution Statement A).\n- Groove dimensions apply to all grooves; the number of grooves depends on the application. Accessory makers often count rail length in slots: an n-slot section is n × .394 in long.\n- The mount-jaw file is the female shape at nominal size with one recoil key: subtract or adapt it for your mount, and add your process clearance on the flanks (a printed clamp typically needs a few tenths of a mm).\n- Weaver rails share the outer shape loosely but have narrower .180 in grooves without a fixed spacing: Weaver accessories usually fit Picatinny, Picatinny accessories often do not fit Weaver.\n\nparameter  value\nwidth across the 45° edges  .835 −.005 in (21.209 mm)\ntop flat (datum C)  .748 ±.002 in (18.999 mm)\nneck width  .617 −.010 in (15.672 mm)\nlower flank  45°, .108 in (2.743 mm) deep (basic)\nupper edge  45° from the top flat to the widest point (1.105 mm)\ntop to neck  .164 −.020 in\nrail height above the mounting surface  .367 in min (9.322 mm)\nrecoil groove width  .206 +.008/−0 in (5.232 mm)\nrecoil groove depth  .118 +.008/−0 in (2.997 mm)\ngroove spacing (centre to centre)  .394 in basic (10.008 mm)\nedge break / fillets  .002 +.010 in / .020 ±.015 in\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- US Army ARDEC (via EverySpec): MIL-STD-1913 (AR): Dimensioning of accessory mounting rail for small arms weapons, 1995 (Distribution A, public release) — web — US Government work, public release — https://everyspec.com/MIL-STD/MIL-STD-1800-1999/MIL-STD-1913_17705/\n- Wikipedia: Picatinny rail (Weaver compatibility) — web — Publisher's page; dimensions are facts — https://en.wikipedia.org/wiki/Picatinny_rail\n\nFree files (CC BY 4.0, Xem Studio; STEP + STL, 6 parts): https://xemstudio.com/files/hardware/picatinny-rail-mil-std-1913/index.json\nAPI: https://xemstudio.com/api/geometry?object=picatinny-rail-mil-std-1913\n",
 "sources": [
  {
   "publisher": "US Army ARDEC (via EverySpec)",
   "title": "MIL-STD-1913 (AR): Dimensioning of accessory mounting rail for small arms weapons, 1995 (Distribution A, public release)",
   "url": "https://everyspec.com/MIL-STD/MIL-STD-1800-1999/MIL-STD-1913_17705/",
   "formats": [
    "web"
   ],
   "license": "US Government work, public release",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Wikipedia",
   "title": "Picatinny rail (Weaver compatibility)",
   "url": "https://en.wikipedia.org/wiki/Picatinny_rail",
   "formats": [
    "web"
   ],
   "license": "Publisher's page; dimensions are facts",
   "license_verified": true,
   "hosted": false
  }
 ],
 "xem": {
  "status": "free-files",
  "sheet_free": true,
  "mesh_price_usd": null,
  "step_price_usd": null,
  "tolerance_mm": null
 },
 "related": [
  "dovetail-rail-mount",
  "streamlight-protac-rail-mount-hl-x",
  "scope-dovetail-rails",
  "bug-a-salt-3-0"
 ],
 "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": "How far apart are Picatinny slots?",
   "a": ".394 in (10.008 mm) centre to centre; each groove is .206 in (5.232 mm) wide and .118 in (2.997 mm) deep."
  },
  {
   "q": "How wide is a Picatinny rail?",
   "a": ".835 in (21.21 mm) across the 45° edges; the top flat is .748 in (19.0 mm) and the neck .617 in (15.67 mm)."
  }
 ],
 "files_license": null,
 "offers": [
  {
   "file": "picatinny-rail-3-slot",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/picatinny-rail-mil-std-1913/picatinny-rail-3-slot.step",
   "stl": "https://xemstudio.com/files/hardware/picatinny-rail-mil-std-1913/picatinny-rail-3-slot.stl",
   "note": "3-slot rail section, 30.02 mm long (3 x .394 in), MIL-STD-1913 profile and grooves, true size"
  },
  {
   "file": "picatinny-rail-5-slot",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/picatinny-rail-mil-std-1913/picatinny-rail-5-slot.step",
   "stl": "https://xemstudio.com/files/hardware/picatinny-rail-mil-std-1913/picatinny-rail-5-slot.stl",
   "note": "5-slot rail section, 50.04 mm long (5 x .394 in), MIL-STD-1913 profile and grooves, true size"
  },
  {
   "file": "picatinny-rail-7-slot",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/picatinny-rail-mil-std-1913/picatinny-rail-7-slot.step",
   "stl": "https://xemstudio.com/files/hardware/picatinny-rail-mil-std-1913/picatinny-rail-7-slot.stl",
   "note": "7-slot rail section, 70.05 mm long (7 x .394 in), MIL-STD-1913 profile and grooves, true size"
  },
  {
   "file": "picatinny-rail-9-slot",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/picatinny-rail-mil-std-1913/picatinny-rail-9-slot.step",
   "stl": "https://xemstudio.com/files/hardware/picatinny-rail-mil-std-1913/picatinny-rail-9-slot.stl",
   "note": "9-slot rail section, 90.07 mm long (9 x .394 in), MIL-STD-1913 profile and grooves, true size"
  },
  {
   "file": "picatinny-rail-13-slot",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/picatinny-rail-mil-std-1913/picatinny-rail-13-slot.step",
   "stl": "https://xemstudio.com/files/hardware/picatinny-rail-mil-std-1913/picatinny-rail-13-slot.stl",
   "note": "13-slot rail section, 130.10 mm long (13 x .394 in), MIL-STD-1913 profile and grooves, true size"
  },
  {
   "file": "picatinny-mount-jaw",
   "formats": [
    "step",
    "stl"
   ],
   "price_usd": 0,
   "license": "CC BY 4.0 (Xem Studio)",
   "step": "https://xemstudio.com/files/hardware/picatinny-rail-mil-std-1913/picatinny-mount-jaw.step",
   "stl": "https://xemstudio.com/files/hardware/picatinny-rail-mil-std-1913/picatinny-mount-jaw.stl",
   "note": "Female profile for designing a mount: block with the MIL-STD-1913 rail removed and a .206 in recoil key; nominal, add clearance"
  }
 ],
 "markdown": "https://xemstudio.com/objects/picatinny-rail-mil-std-1913/index.md"
}