Measure underbust and overbust, not your regular bra size.

Yes, it’s straightforward, but most people mess it up by assuming their bra size translates directly to bikini tops.

Grab a soft measuring tape. First, measure your underbust (right under your boobs, snug but not tight). Then measure your overbust at the fullest part of your chest, keeping the tape parallel. Subtract the difference — each inch is roughly one cup size (1 inch = A, 2 = B, etc.). That gives you a starting point.

But here’s the thing: bikini sizing is not standardized at all. A small in one brand might be a medium in another. Your bra size is a good guide, but the cut matters — a triangle top fits differently than a balconette. If you’re buying online, check the brand’s size chart and reviews that mention fit. And if you’re between sizes, size up. Bikini tops shouldn’t cut into your shoulders.

Or just order two sizes and return the one that doesn’t fit.