3.5 in floppy disk (90 mm diskette) — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/3-5-inch-floppy-disk-90-mm/  (CC BY 4.0)
Basis: ECMA-147 (ISO/IEC 9529-1), 90 mm flexible disk cartridge, 1.44 MB high density (ISO Type 303)
Catalog version: 2026-10-20

Overall (mm): length 94.0, width 90.0, height 3.3
- 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.

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.

Files elsewhere (not hosted by Xem Studio; license as stated by the publisher):
- Ecma International: ECMA-147: 90 mm flexible disk cartridges, ISO Type 303 (PDF) — web — Publisher's page; dimensions are facts — https://ecma-international.org/wp-content/uploads/ECMA-147_1st_edition_december_1990.pdf

Free files (CC BY 4.0, Xem Studio; STEP + STL, 1 parts): https://xemstudio.com/files/hardware/3-5-inch-floppy-disk-90-mm/index.json
API: https://xemstudio.com/api/geometry?object=3-5-inch-floppy-disk-90-mm