Let's get straight to it — here's what actually matters on this one.

• Size for your shoulders first, then have the waist taken in — sizing down for the waist usually means the shoulder seams sit inches inward, restricting arm movement.
• Look for 'athletic fit' or 'muscle fit' labels, which are cut with more shoulder and chest room but a trimmer waist than regular fit.
• Raglan and set-in sleeve construction differ — set-in sleeves (most dress shirts) show shoulder-fit problems more visibly than raglan cuts.
• A shoulder seam sitting an inch past your actual shoulder bone will pull and crease every time you move your arms, wearing out that seam faster.

The fit-and-fabric-health takeaway: A too-narrow shoulder doesn't just look wrong — the constant fabric pull at the seam increases friction against skin at the exact point your arm moves most.

Next up: check out our guide on our fit guide for shorter men.