I have the unfortunate task of writing a technical document, and I know the government is a stickler for unnecessary detail. Is there standard name for the standard computer screw? Also, what is the name of the standard disk drive screw?

4 Answers 4


Most screws in a computer are UTS 6-32 screws. 6-32 screws are used for your power supply, 3.5" hard drives, securing expansion cards, and the case panels.

The other common screw type is the metric M3×0.5 screw, which are used for mounting optical drives, floppy drives, and the motherboard.

The thread size for an NVMe drive is usually M2×0.4, although many drives are secured with a tool-free design nowadays, typically a plastic lever which rotates.

To make it harder, there are also computer cases that ship with motherboard standoffs that accept imperial screws, not M3.

It's amusing that both imperial and metric screws are used in each computer, and rather annoying that these screws are fairly similar in size (although not in threading). This means that an M3 screw will fit in a 6-32 hole, and will even seem to screw in, but it won't stay in place well. A 6-32 screw will go in an M3 hole if you try hard enough, which results in stripping.

Note that the self-tapping plastic screws used exclusively for fans and some lighting are also standardized, although they're just standardized within industry as "self-tapping plastic screws" rather than being a standard mechanical screw size.

Side-by-side comparison of a UNC 6-32 and an M3 screw showing their slight difference in diameter and thread pitch

  • 5
    Great answer but I disagree about case fan screws being standardized. I have four or five different kinds in my build box. They vary in thread pitch, shaft size, head size, some have a self-tapping gouge taken out of the tip. Woe betide anyone who tries to put one of the thicker ones into a fan with smaller-than-average holes. Because of this I prefer to use the black two-part plastic expanding rivets where possible. Aug 22, 2011 at 7:18
  • 18
    Oh wow, there's an entire WikiPedia article on computer screws...
    – Pylsa
    Aug 22, 2011 at 11:17
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    @Matias Nino: there are the laptop HDD screws which are tiny and have flat heads.
    – Daniel
    Aug 22, 2011 at 14:17
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    3.5" HDDs use 6-32, but 2.5" SSDs use M3. May 2, 2016 at 16:46
  • 1
    Hex-head screws in your PC will be #6-32 99% of the time (obvious exception is right there in the picture in this answer), but frustratingly round/pan-head screws in your PC will be 3mm perhaps only 60% of the time. (Regarding that picture: I can't find M3 machine screws with a dual socket/phillips drive anywhere online, I'm not sure where they sourced that one from!) Oct 25, 2017 at 23:23

6-32, and M3.

"Computer case screws"

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    I thought they were all M3s.. which would explain some issue i've had in the past... +1 for enlightenment!
    – Journeyman Geek
    Aug 22, 2011 at 3:56

Here are the specs for most computer screws (Laptops are different)

Just Google "Computer Screw Set" and you will find kits that have everything you need.

Any special screws will come with the hardware you purchase.

Main board conventional copper column (M3 x 6 + 6)

Main board fixed screws (M3 x 5)

Main board insulation gasket (red M3 x 8)

CD-ROM set screws (M3 x 4)

Hard drive screw (M3.5 x 5)

Chassis hand twist screws (silver M3.5 x 5)

Chassis hand twist screw (black M3.5 x 5)

Chassis high-strength screw (M3.5 x 6)

Conventional chassis fan retaining screw (white zinc M5 x 10)

Conventional chassis fans retaining screw (black M5 x 10)


One thing not mentioned here is about #4-40 and optical drives. I haven't looked into screw sizes for many years, but I ran into this fact many years ago, i'm not sure to what extent it apples nowadays. It may still apply.

It's mentioned here

https://www.overclock.net/forum/18082-builds-logs-case-mods/605048-dvd-drive-screw-size.html (post from july 2009)

"Actually optical drives don't use the same 6-32 screws that everything else does. Most of them use M3x5, 0.5mm pitch screws, some use #4-40 screws."

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