Under Armour to American Eagle size
The short answer
Under Armour SM is American Eagle XS by the two brands' own charts. 4 of 7 Under Armour sizes land on a different label at American Eagle.
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 | American Eagle, by chart | Same label | American Eagle builds it for | American Eagle also prints |
|---|---|---|---|---|---|
| XS | chest 31 to 34 in, waist 28 to 29 in | XS | XS | chest 35 to 36 in, neck 13.5 to 14 in, sleeve 31.5 in | not published |
| SM | chest 34 to 37 in, waist 29 to 31 in | XS | not published | chest 35 to 36 in, neck 13.5 to 14 in, sleeve 31.5 in | not published |
| MD | chest 37 to 41 in, waist 31 to 34 in | S | not published | chest 37 to 39 in, neck 14.5 to 15 in, sleeve 32.5 in | not published |
| LG | chest 41 to 44 in, waist 34 to 37 in | M | not published | chest 40 to 42 in, neck 15 to 15.5 in, sleeve 33.5 in | not published |
| XL | chest 44 to 48 in, waist 37 to 41 in | XL | XL | chest 46 to 48 in, neck 16.5 to 17 in, sleeve 35.5 in | not published |
| XXL | chest 48 to 52 in, waist 41 to 45.5 in | XXL | XXL | chest 49 to 51 in, neck 17 to 18 in, sleeve 36.5 in | not published |
| 3XL | chest 52 to 56 in, waist 45.5 to 50 in | XXXL | XXXL | chest 52 to 54 in, neck 18 to 19 in, sleeve 37 in | 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
- American Eagle size guide, read on 2026-09-18. American Eagle on TrueToSize