A simple at-home measuring routine to help you find a more comfortable bra band and cup starting point.
Knowing your actual measurements before you shop saves time and cuts down on returns, since you can compare numbers directly against a brand's size chart instead of guessing from a label alone. It also gives you a starting point if your size has changed due to weight fluctuation, age, or time since your last professional fitting.
All you need is a soft measuring tape and a well-fitting, unpadded bra or no bra at all. A mirror helps you check that the tape stays level and snug without digging in, and doing this in front of one makes the whole process more accurate.
Wrap the tape directly under your bust, around your ribcage, keeping it level and snug but not tight. Round to the nearest whole number, and if the result is odd, round up to the nearest even number for your band size.
Wrap the tape around the fullest part of your bust, usually across the nipple line, keeping the tape parallel to the floor and not pulled tight. This number, taken alongside your band measurement, is what determines your cup size.
Subtract your band measurement from your bust measurement. Each inch of difference typically corresponds to one cup size, so a one-inch difference is an A cup, two inches is a B cup, and so on, though this can vary slightly between brands.
A band that rides up in the back, straps that constantly slip, cups that gape or overflow, and underwire that doesn't sit flat against your ribcage are all common signs that your current size no longer fits.
Your calculated size is a starting point, not a guarantee, since fit varies between styles and brands. Try on a few sizes around your calculated measurement and check how the band, cups, and straps sit before deciding.
Balconette, plunge, and full-coverage styles can all fit differently even in the same labeled size, so it's normal to need a slightly different size depending on the cut. Adjustable straps and multiple hook-and-eye rows also give you room to fine-tune fit within a single bra.
Measuring over a thick or padded bra, pulling the tape too tight, or letting it ride up at an angle in the back are the most common causes of an inaccurate result. Measuring twice and averaging the results helps catch these errors.
Once you know your measurements, jot down both numbers along with which brands and styles have fit you well in the past. This makes future shopping faster and helps you spot patterns in which cuts consistently work for your shape.