Reformation to Under Armour clothing size
The short answer
Reformation S is Under Armour SM by the two brands' own charts. 6 of 8 Reformation 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.
| Reformation | Reformation builds it for | Under Armour, by chart | Same label | Under Armour builds it for | Under Armour also prints |
|---|---|---|---|---|---|
| XS | bust 33 in, waist 25 in, hip 36 in | XS | XS | bust 32.5 to 33.5 in, waist 25.5 to 27 in | US 0-2 |
| S | bust 35 in, waist 27 in, hip 38 in | SM | not published | bust 33.5 to 36 in, waist 27 to 29 in | US 4-6 |
| M | bust 37 in, waist 29 in, hip 40 in | MD | not published | bust 36 to 38 in, waist 29 to 31 in | US 8-10 |
| L | bust 39.5 in, waist 31.5 in, hip 42.5 in | LG | not published | bust 38 to 41 in, waist 31 to 34 in | US 12-14 |
| XL | bust 41.5 in, waist 33.5 in, hip 44.5 in | XL | XL | bust 41 to 44 in, waist 34 to 37 in | US 16 |
| 1X | bust 45 in, waist 37.5 in, hip 47.5 in | XXL | not published | bust 44 to 47 in, waist 37 to 40 in | US 18 |
| 2X | bust 48 in, waist 40.5 in, hip 50.5 in | 3XL | not published | bust 47 to 50 in, waist 40 to 43 in | US 20 |
| 3X | bust 51 in, waist 43.5 in, hip 53.5 in | 3XL | not published | bust 47 to 50 in, waist 40 to 43 in | US 20 |
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
- Reformation size guide, read on 2026-09-18. Reformation on TrueToSize
- Under Armour size guide, read on 2026-09-18. Under Armour on TrueToSize