Bangle sizing requires measuring the hand, not the wrist — and this is the source of most bangle fit problems. The wrist is narrower than the knuckles when the hand is closed, so measuring the wrist and ordering a bracelet-equivalent size produces a bangle that won't fit over the hand. The correct measurement is the circumference of the closed hand at its widest point: press the fingers together and thumb against the palm, measure around the knuckles. A bangle sized this way will be slightly loose on the wrist, which is appropriate — bangles are meant to slide along the forearm within a range, not sit fixed at one point.
Thin bangles and wide bangles serve different purposes. A thin bangle (2–3mm width) is designed for stacking: individually it's a delicate, barely-there piece; accumulated, five or seven thin bangles create a lush, layered look with significant collective weight and sound. Wide bangles (8mm and above) are statement pieces on their own — the width is the design, and a single wide bangle worn alone is sufficient to make a wrist presence. The most effective stacking looks combine thin bangles of slightly varied texture and finish, not uniform pieces.
Hollow bangles deserve a specific consideration that hollow chains don't: bangles stack and contact each other continuously. Every time two hollow bangles slide past each other, the outer surfaces abrade slightly. Over years of daily stacking wear, this contact wears the surface of hollow bangles noticeably more than hollow chains experience. For a bangle collection intended to grow over time and be worn daily, starting with solid construction establishes a durable base. For occasional wear or smaller stacks, hollow bangles are a practical choice.