Whistles to GU clothing size
The short answer
Whistles 12 is GU XL by the two brands' own charts.
Both brands publish the body bust each size is cut for, so every row matches a bust, not a letter or a number.
| Whistles | Whistles builds it for | GU Japan sizing, by chart | Same label | GU builds it for | GU also prints |
|---|---|---|---|---|---|
| 04 | bust 30 in, waist 23.5 in, hip 34.5 in | S | not published | bust 29.5 to 31.5 in, waist 23.2 to 24.8 in, hip 31.9 to 33.5 in | not published |
| 06 | bust 31 in, waist 24.5 in, hip 35.5 in | S | not published | bust 29.5 to 31.5 in, waist 23.2 to 24.8 in, hip 31.9 to 33.5 in | not published |
| 08 | bust 32 in, waist 25.5 in, hip 36.5 in | M | not published | bust 31.5 to 33.5 in, waist 24.8 to 26.4 in, hip 33.5 to 35 in | not published |
| 10 | bust 34 in, waist 27.5 in, hip 38.5 in | L | not published | bust 33.5 to 35.4 in, waist 26.4 to 28 in, hip 35 to 36.6 in | not published |
| 12 | bust 36 in, waist 29.5 in, hip 40.5 in | XL | not published | bust 35.4 to 37.8 in, waist 28 to 30.3 in, hip 36.6 to 38.6 in | not published |
| 14 | bust 38 in, waist 31.5 in, hip 42.5 in | XXL | not published | bust 37.8 to 40.2 in, waist 30.3 to 32.7 in, hip 38.6 to 40.6 in | not published |
| 16 | bust 40 in, waist 33.5 in, hip 44.5 in | XXL | not published | bust 37.8 to 40.2 in, waist 30.3 to 32.7 in, hip 38.6 to 40.6 in | not published |
| 18 | bust 42.5 in, waist 35.5 in, hip 46.5 in | 3XL | not published | bust 40.2 to 43.3 in, waist 32.7 to 35.4 in, hip 40.6 to 43.3 in | not published |
| 20 | bust 45 in, waist 38 in, hip 49 in | not made | not published | not published | not published |
What wearers say
Charts describe a garment, not a fit. We do not collect fit reports for this category yet, so this table is the two brands' own claims and nothing more.
Sources
- Whistles size guide, read on 2026-09-18.
- GU Japan sizing size guide, read on 2026-09-25.