# 5.25 in floppy disk (130 mm minifloppy)

> What are the exact dimensions of a 5.25 inch floppy disk?

- Category: Vintage forms › Retro media · 1985
- Kind: Modern device
- Basis: ECMA-99, 130 mm flexible disk cartridge, 1.2 MB high density
- Page: https://xemstudio.com/objects/5-25-inch-floppy-disk-130-mm/ · JSON: https://xemstudio.com/api/geometry?object=5-25-inch-floppy-disk-130-mm · Plain text: https://xemstudio.com/objects/5-25-inch-floppy-disk-130-mm/sheet.txt
- License: dimension sheet CC BY 4.0 (Xem Studio); linked files under their publishers' licenses
- Use in every chat: add https://xemstudio.com/mcp as a connector (https://xemstudio.com/use-with-ai/)

## Overall (mm)

| length | width | height |
|---|---|---|
| 133.3 | 133.3 | 2.1 |

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

## Notes

- A 5.25 inch floppy disk jacket is a 133.3 mm square (l1 = 133.3 ±0.4 mm, corners 90° ±30′) and between 1.2 and 2.1 mm thick overall (ECMA-99 §3.1). The central window is Ø39.7 ±0.2 mm, centred 66.65 mm from the reference edge — the middle of the jacket.
- ECMA-99 is the 1.2 MB high-density disk; the 360 KB double-density disk is specified in ECMA-78. Write-protect notch size is not in this standard's text.
- The file is the jacket at the published size: 133.3 × 133.3 mm, drawn 2.1 mm thick (the standard's maximum overall thickness), with the Ø39.7 mm central window at the jacket centre; no printing allowance. Index and head windows are listed above but not modelled. 

## Sizes

| dimension | value |
|---|---|
| jacket side (l1) | 133.3 mm ±0.4 |
| corner angle | 90° ±30′ |
| overall thickness (e2) | over 1.2 mm, under 2.1 mm |
| gauge | falls freely through a 2.6 mm slot, 150 mm deep |
| central window (d1) | Ø39.7 mm |
| central window centre (l2) | 66.65 mm ±0.30 from the reference edge |
| index window (d2) | Ø6.35 mm ±0.20 at l3 42.10 / l4 60.00 mm ±0.25 |
| head window | 12.7 mm ±0.2 wide × 35.00 mm ±0.25 long, R6.35 ends, lowest point 3.30 mm ±0.25 from the reference edge |
| optional notches | inside 48.0 mm min. to 58.0 mm max. along the reference edge |

## Where the files are

- Ecma International: [ECMA-99 (PDF)](https://ecma-international.org/wp-content/uploads/ECMA-99_1st_edition_september_1985.pdf) — web — Publisher's page; dimensions are facts

## Free STEP/STL (1 parts, CC BY 4.0, Xem Studio)

Index: https://xemstudio.com/files/hardware/5-25-inch-floppy-disk-130-mm/index.json

- 5-25-inch-floppy-disk-130-mm-jacket: [STEP](https://xemstudio.com/files/hardware/5-25-inch-floppy-disk-130-mm/5-25-inch-floppy-disk-130-mm-jacket.step) · [STL](https://xemstudio.com/files/hardware/5-25-inch-floppy-disk-130-mm/5-25-inch-floppy-disk-130-mm-jacket.stl) — Jacket 133.3 mm square × 2.1 mm, Ø39.7 central window (ECMA-99 nominal)

## Questions

**How big is a 5.25 inch floppy disk?**

The jacket is 133.3 mm square and under 2.1 mm thick, with a Ø39.7 mm centre window (ECMA-99).

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