Port Authority vs Under Armour: which size fits the same?
In polos, a Port Authority L is closest to an Under Armour L (1″ roomier).
Polos
Under Armour polos measure about ¾″ more around than Port Authority at the same size. A Port Authority L is closest to an Under Armour L (1″ roomier).
| Port Authority | Chest · length | Closest Under Armour | Chest · length | Under Armour is |
|---|---|---|---|---|
| Port Authority XS | 36½″ · 27½″ | none close | ||
| Port Authority S | 39½″ · 28½″ | Under Armour S | 40½″ · 29″ | 1″ roomier |
| Port Authority M | 42½″ · 29½″ | Under Armour M | 43½″ · 29½″ | 1″ roomier |
| Port Authority L | 45½″ · 30½″ | Under Armour L | 46½″ · 30″ | 1″ roomier |
| Port Authority XL | 48½″ · 31¼″ | Under Armour XL | 49½″ · 31″ | 1″ roomier |
| Port Authority XXL | 51½″ · 32¼″ | Under Armour XXL | 52½″ · 32″ | 1″ roomier |
| Port Authority 3XL | 55½″ · 32¾″ | Under Armour 3XL | 55½″ · 33″ | the same around |
From Port Authority: Port Authority Silk Touch Polo (K500), Port Authority Dry Zone UV Micro-Mesh Polo (K110), Port Authority Core Classic Pique Polo (K100). From Under Armour: Under Armour Tech Polo (1370399). Relaxed and oversized cuts are left out.
More: Port Authority sizing · Under Armour sizing
Get your exact size in any of these
Add three shirts you own that fit well. FitCard compares their real measurements with every shirt here and tells you the one size to buy, and why, in terms of your own shirts. Free, no tape measure.
Garment measurements: the shirt itself, chest all the way around and length from shoulder to hem, from each brand's own chart or wholesale spec sheet, checked November 2026. Shirts with half or more cotton are shown as they come out of a dryer (about 2% less around and 4% shorter). Brands change their cuts, so check the shop's chart before you buy.