You know the disappointment: you order your normal tee, and it fits like a tent—or worse, like a hand-me-down. Oversized is supposed to look easy, but it actually takes a little math. The good news? You don't need to be a tailor. You just need two numbers: your chest circumference and the body length you're comfortable with.

Measure your chest at the fullest part, keeping the tape level. That number tells you which size to start with. Windbar's size chart lists chest width for each size, and for an oversized fit, you'll want that width to be 2–4 inches larger than your actual chest. If your chest is 40 inches, a tee with a 44-inch chest is going to give you that relaxed, drapey look without swimming in fabric.