GU to Under Armour clothing size
The short answer
GU S is Under Armour XXS by the two brands' own charts. 6 of 6 GU sizes land on a different label at Under Armour.
Both brands publish the body bust each size is cut for, so every row matches a bust, not a letter or a number.
On 3 sizes the charts land two or more sizes from the same label. Brands do not measure the body the same way, so on those rows treat the chart answer and the same label as the two ends of a range.
| GU Japan sizing | GU builds it for | Under Armour, by chart | Same label | Under Armour builds it for | Under Armour also prints |
|---|---|---|---|---|---|
| XS | bust 27.6 to 29.5 in, waist 21.3 to 23.2 in, hip 30.3 to 31.9 in | not made | XS | not published | not published |
| S | bust 29.5 to 31.5 in, waist 23.2 to 24.8 in, hip 31.9 to 33.5 in | XXS | not published | bust 31 to 32.5 in, waist 24.5 to 25.5 in | US 00 |
| M | bust 31.5 to 33.5 in, waist 24.8 to 26.4 in, hip 33.5 to 35 in | XXS | not published | bust 31 to 32.5 in, waist 24.5 to 25.5 in | US 00 |
| L | bust 33.5 to 35.4 in, waist 26.4 to 28 in, hip 35 to 36.6 in | SM | not published | bust 33.5 to 36 in, waist 27 to 29 in | US 4-6 |
| XL | bust 35.4 to 37.8 in, waist 28 to 30.3 in, hip 36.6 to 38.6 in | MD | XL | bust 36 to 38 in, waist 29 to 31 in | US 8-10 |
| XXL | bust 37.8 to 40.2 in, waist 30.3 to 32.7 in, hip 38.6 to 40.6 in | LG | XXL | bust 38 to 41 in, waist 31 to 34 in | US 12-14 |
| 3XL | bust 40.2 to 43.3 in, waist 32.7 to 35.4 in, hip 40.6 to 43.3 in | XL | 3XL | bust 41 to 44 in, waist 34 to 37 in | US 16 |
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
- GU Japan sizing size guide, read on 2026-09-25.
- Under Armour size guide, read on 2026-09-18. Under Armour on TrueToSize