Brooks Convertible 2.0 Sports Bra

You’ll need a flexible tape measure. It’s also best to wear a bra that doesn’t change your shape — no padding or compression. You can also just skip the bra.

1. Measure your rib cage
   Start your measurements by finding your band size. Measure around your rib cage where the bottom band would sit. The tape measure should feel quite snug. If you get a fraction, round down to the nearest inch. Using this chart, find your corresponding band size based on your measurement.
   
2. Measure your bust
   Next, find your cup size. Measure around the fullest part of your boobs — which may not be the center — and round up to the nearest inch. Then subtract your rib cage measurement. The difference in inches is your suggested cup size. If you get a fraction, round up to the larger size.