# 3.5 in floppy disk (90 mm diskette)

> What are the exact dimensions of a 3.5 inch floppy disk?

- Category: Vintage forms › Retro media · 1990
- Kind: Modern device
- Basis: ECMA-147 (ISO/IEC 9529-1), 90 mm flexible disk cartridge, 1.44 MB high density (ISO Type 303)
- Page: https://xemstudio.com/objects/3-5-inch-floppy-disk-90-mm/ · JSON: https://xemstudio.com/api/geometry?object=3-5-inch-floppy-disk-90-mm · Plain text: https://xemstudio.com/objects/3-5-inch-floppy-disk-90-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 |
|---|---|---|
| 94.0 | 90.0 | 3.3 |

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

## Notes

- A 3.5 in floppy disk case is 94.0 × 90.0 × 3.3 mm (ECMA-147 §6.1: L1 = 94.0 ±0.3 mm, L2 = 90.0 +0.4/−0.1 mm, thickness E1 = 3.3 ±0.2 mm in the 8.5 mm bands along the two edges). Three corners are R2.0 ±1.0 mm, the fourth is cut at 45° ±2°, and the case edges are rounded R0.40 ±0.25 mm.
- The hub access hole on side 0 is Ø26.50 mm min., centred 40.00 × 31.00 mm (±0.15) from the reference axes, which pass through the primary locating hole (Ø3.6 ±0.1 mm). The secondary locating hole is 80.0 ±0.2 mm along the X axis, 3.6 × 4.4 mm. Head windows are 9.00 ±0.20 mm wide.
- The file is the case at the published size: a 94.0 × 90.0 × 3.3 mm plate with R2.0 corners, no printing allowance. The 45° corner, shutter, holes and label recess are placed by the standard's figures, not its text, so they are not modelled; build around the envelope and check a real disk.
- ECMA-147 covers the 1.44 MB high-density disk; the 720 KB double-density disk is ECMA-125 (ISO/IEC 8860). Makers' shells may differ in shutter and label detail inside these limits — a measured Xem scan of the shutter and write-protect slide is planned.

## Sizes

| dimension | value |
|---|---|
| case length (L1) | 94.0 mm ±0.3 |
| case width (L2) | 90.0 mm +0.4 / −0.1 |
| thickness (E1) | 3.3 mm ±0.2 |
| corner radius, three corners (R1) | 2.0 mm ±1.0 |
| fourth corner | 45° ±2° |
| case edge radius (R2) | 0.40 mm ±0.25 |
| hub access hole (D1) | Ø26.50 mm min. |
| hub hole centre from reference axes | 40.00 × 31.00 mm ±0.15 |
| primary locating hole (D2) | Ø3.6 mm ±0.1 |
| secondary locating hole | 3.6 × 4.4 mm, 80.0 mm ±0.2 along X |
| head window width (L18) | 9.00 mm ±0.20 |
| label area | L11 3.5 mm min., L12 76.5 mm max. |

## Where the files are

- Ecma International: [ECMA-147: 90 mm flexible disk cartridges, ISO Type 303 (PDF)](https://ecma-international.org/wp-content/uploads/ECMA-147_1st_edition_december_1990.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/3-5-inch-floppy-disk-90-mm/index.json

- 3-5-inch-floppy-disk-90-mm-case: [STEP](https://xemstudio.com/files/hardware/3-5-inch-floppy-disk-90-mm/3-5-inch-floppy-disk-90-mm-case.step) · [STL](https://xemstudio.com/files/hardware/3-5-inch-floppy-disk-90-mm/3-5-inch-floppy-disk-90-mm-case.stl) — Case 94.0 × 90.0 × 3.3 mm, R2.0 corners (ECMA-147 nominal; shutter and holes not modelled)

## Questions

**How big is a 3.5 inch floppy disk?**

94.0 × 90.0 × 3.3 mm (ECMA-147): three R2.0 corners and one 45° corner.

**Is a 3.5 inch floppy really 3.5 inches?**

No: the disk inside is 90 mm; the case is 94.0 × 90.0 mm (3.70 × 3.54 in).

## Fits with

- [5.25 in floppy disk (130 mm minifloppy)](https://xemstudio.com/objects/5-25-inch-floppy-disk-130-mm/)
- [8 in floppy disk (200 mm)](https://xemstudio.com/objects/8-inch-floppy-disk-200-mm/)
- [CD / DVD disc Ø120 × 1.2 mm with Ø15 hole (and mini CD Ø80)](https://xemstudio.com/objects/cd-dvd-discs/)