Under Armour to GU size
The short answer
Under Armour XS is GU S by the two brands' own charts. 6 of 6 Under Armour sizes land on a different label at GU.
Both brands publish the body chest each size is cut for, so every row matches a chest, not a letter.
| Under Armour | Under Armour builds it for | GU Japan sizing, by chart | Same label | GU builds it for | GU also prints |
|---|---|---|---|---|---|
| XS | chest 31 to 34 in, waist 28 to 29 in | S | XS | chest 31.5 to 34.7 in, waist 26.8 to 29.9 in | not published |
| SM | chest 34 to 37 in, waist 29 to 31 in | M | not published | chest 34.7 to 37.8 in, waist 29.9 to 33.1 in | not published |
| MD | chest 37 to 41 in, waist 31 to 34 in | L | not published | chest 37.8 to 40.9 in, waist 33.1 to 36.2 in | not published |
| LG | chest 41 to 44 in, waist 34 to 37 in | XL | not published | chest 40.9 to 44.1 in, waist 36.2 to 39.4 in | not published |
| XL | chest 44 to 48 in, waist 37 to 41 in | XXL | XL | chest 44.1 to 47.2 in, waist 39.4 to 42.5 in | not published |
| XXL | chest 48 to 52 in, waist 41 to 45.5 in | 3XL | XXL | chest 47.2 to 50.4 in, waist 42.5 to 45.7 in | not published |
| 3XL | chest 52 to 56 in, waist 45.5 to 50 in | not made | 3XL | not published | not published |
| 4XL | chest 56 to 60 in, waist 50 to 54.5 in | not made | not published | not published | not published |
| 5XL | chest 60 to 64 in, waist 54.5 to 59 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
- Under Armour size guide, read on 2026-09-18. Under Armour on TrueToSize
- GU Japan sizing size guide, read on 2026-09-25.