Under Armour to Old Navy size
The short answer
Under Armour SM is Old Navy XS by the two brands' own charts. 8 of 8 Under Armour sizes land on a different label at Old Navy.
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 | Old Navy, by chart | Same label | Old Navy builds it for | Old Navy also prints |
|---|---|---|---|---|---|
| XS | chest 31 to 34 in, waist 28 to 29 in | not made | XS | not published | not published |
| SM | chest 34 to 37 in, waist 29 to 31 in | XS | not published | chest 36 to 37 in, neck 13 to 13.5 in, sleeve 31.5 to 32 in | not published |
| MD | chest 37 to 41 in, waist 31 to 34 in | S | not published | chest 38 to 39 in, neck 14 to 14.5 in, sleeve 32.5 to 33 in | not published |
| LG | chest 41 to 44 in, waist 34 to 37 in | M or L | not published | chest 40 to 42 in, neck 15 to 15.5 in, sleeve 33.5 to 34 in | not published |
| XL | chest 44 to 48 in, waist 37 to 41 in | L | XL | chest 44 to 46 in, neck 16 to 16.5 in, sleeve 34.5 to 35 in | not published |
| XXL | chest 48 to 52 in, waist 41 to 45.5 in | XL | XXL | chest 48 to 50 in, neck 17 to 17.5 in, sleeve 35.5 to 36 in | not published |
| 3XL | chest 52 to 56 in, waist 45.5 to 50 in | XXL or XXXL | XXXL | chest 51 to 53 in, neck 18 to 18.5 in, sleeve 36.5 to 37 in | not published |
| 4XL | chest 56 to 60 in, waist 50 to 54.5 in | XXXXL | XXXXL | chest 58 to 60 in, neck 20.5 to 21 in, sleeve 38.5 to 39 in | not published |
| 5XL | chest 60 to 64 in, waist 54.5 to 59 in | XXXXL | not published | chest 58 to 60 in, neck 20.5 to 21 in, sleeve 38.5 to 39 in | 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
- Old Navy size guide, read on 2026-09-18. Old Navy on TrueToSize