# Picatinny rail (MIL-STD-1913): profile, grooves and mount jaw

> What are the exact Picatinny rail dimensions (MIL-STD-1913)?

- Category: Hardware › Mounting standards
- Kind: Standard part
- Basis: MIL-STD-1913 (AR), Figures 1 and 2 (public release)
- Page: https://xemstudio.com/objects/picatinny-rail-mil-std-1913/ · JSON: https://xemstudio.com/api/geometry?object=picatinny-rail-mil-std-1913 · Plain text: https://xemstudio.com/objects/picatinny-rail-mil-std-1913/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); files CC BY 4.0 or their publisher's license
- Use in every chat: add https://xemstudio.com/mcp as a connector (https://xemstudio.com/use-with-ai/)

## Overall (mm)

| width | height |
|---|---|
| 21.209 | 9.322 |

**Exact dimensions.** True size, with no printing tolerance added.

## 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.

## Sizes

| parameter | value |
|---|---|
| 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 |

## Where the files are

- US Army ARDEC (via EverySpec): [MIL-STD-1913 (AR): Dimensioning of accessory mounting rail for small arms weapons, 1995 (Distribution A, public release)](https://everyspec.com/MIL-STD/MIL-STD-1800-1999/MIL-STD-1913_17705/) — web — US Government work, public release
- Wikipedia: [Picatinny rail (Weaver compatibility)](https://en.wikipedia.org/wiki/Picatinny_rail) — web — Publisher's page; dimensions are facts

## Free STEP/STL (6 parts, CC BY 4.0, Xem Studio)

Index: https://xemstudio.com/files/hardware/picatinny-rail-mil-std-1913/index.json

- picatinny-rail-3-slot: [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) — 3-slot rail section, 30.02 mm long (3 x .394 in), MIL-STD-1913 profile and grooves, true size
- picatinny-rail-5-slot: [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) — 5-slot rail section, 50.04 mm long (5 x .394 in), MIL-STD-1913 profile and grooves, true size
- picatinny-rail-7-slot: [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) — 7-slot rail section, 70.05 mm long (7 x .394 in), MIL-STD-1913 profile and grooves, true size
- picatinny-rail-9-slot: [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) — 9-slot rail section, 90.07 mm long (9 x .394 in), MIL-STD-1913 profile and grooves, true size
- picatinny-rail-13-slot: [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) — 13-slot rail section, 130.10 mm long (13 x .394 in), MIL-STD-1913 profile and grooves, true size
- picatinny-mount-jaw: [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) — Female profile for designing a mount: block with the MIL-STD-1913 rail removed and a .206 in recoil key; nominal, add clearance

## Questions

**How far apart are Picatinny slots?**

.394 in (10.008 mm) centre to centre; each groove is .206 in (5.232 mm) wide and .118 in (2.997 mm) deep.

**How wide is a Picatinny rail?**

.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).

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