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

• Slim fit trims fabric at the chest, waist, and arms for a closer silhouette — best if you carry weight evenly and want a tailored look.
• Regular fit leaves more room through the body and sleeves, better for broader builds or anyone who wants to layer underneath.
• The fastest test: pinch the fabric at your waist while the shirt is buttoned — more than a fist of extra fabric means it's too loose; if you can't pinch any, it's too tight.
• Slim fit in the wrong fabric (stiff cotton-poly blends) restricts movement and traps heat against skin far more than regular fit in the same fabric.

The fit-and-fabric-health takeaway: A slim cut only works with a fabric that has some give and breathes — a slim, stiff, non-breathable shirt is the worst combination for comfort.

Next up: check out our guide on how to find your correct trouser size.