How to Measure for an AA or A Cup Bra

Quick Answer

To measure for an AA or A cup bra, first measure your underbust in inches to get your band size, then measure your bust at the fullest point. The difference between the two determines your cup size—less than 1 inch typically indicates an AA cup, while 1 inch corresponds to an A cup. Always re-measure with a soft tape measure and no padding for the most accurate result.

Why Accurate Measurement Matters for Small Busts

For small busts, even a half-inch difference can change your cup size. Many women with AA or A cups wear bras that are too big in the band and too small in the cup, leading to gaping and lack of support. Measuring correctly helps you choose a bra that fits snugly without being tight.

A well-fitted bra not only looks better but also feels more comfortable. When the band is correct and the cups are the right size, you get the support you need without straps digging in or cups riding up. This is especially important for petite frames where proportion matters.

What You Need to Measure

Grab a soft measuring tape, a mirror, and a piece of paper to note your numbers. Wear a non-padded bra or no bra at all to get the most accurate bust measurement. Stand straight with your arms relaxed at your sides.

If you don't have a measuring tape, use a piece of string and a ruler. Wrap the string around your body, mark the point where it meets, then measure the length with a ruler. This works just as well.

Understanding Your Band Size

Your band size is the foundation of a good fit. Measure around your ribcage, just under your bust, ensuring the tape is level and snug. Round to the nearest whole number. If the measurement is even, that's your band size; if it's odd, add 4 or 5 inches to get the standard band size.

For example, if you measure 28 inches, your band size is 28. If you measure 29 inches, you might need a 32 band, but many small-bust brands offer 30 bands for a better fit. Always check the brand's size chart, as sizing can vary.

Calculating Your Cup Size

Measure around the fullest part of your bust, keeping the tape level and not too tight. Subtract your band size from this bust measurement. The difference in inches corresponds to your cup size: less than 1 inch is AA, 1 inch is A, 2 inches is B, and so on.

For example, if your band size is 30 and your bust measures 31 inches, the 1-inch difference indicates an A cup. If your bust measures 30.5 inches, you might be an AA. This calculation is a starting point; try on bras to confirm the fit.

Adjusting for Your Body Shape

Breast shape affects how a bra fits. Close-set breasts may need a bra with a lower center gore, while wide-set breasts might benefit from a demi cup that pulls tissue forward. Your band size and cup size are only part of the equation.

If you're between sizes, consider a bra with removable padding to customize the fit. This is especially helpful if one breast is slightly larger than the other, as you can adjust each cup individually.

Step-by-Step Measuring Guide

1. Measure Your Band: Wrap the tape around your ribcage, just under your bust. Keep it snug and level. Round to the nearest whole number. If it's odd, add 4-5 inches to get your band size. Checkpoint: The tape should be tight enough that it doesn't slide, but not so tight that it digs in.
2. Measure Your Bust: Wrap the tape around the fullest part of your bust, keeping it level. Do not pull too tight—let it rest naturally. Checkpoint: The tape should be parallel to the floor all the way around.
3. Calculate Cup Size: Subtract your band size from your bust measurement. The difference in inches determines your cup: less than 1 inch = AA, 1 inch = A, 2 inches = B. Checkpoint: If you get a half-inch, round up to the nearest whole number for a more accurate cup size.
4. Try It On: Use your measurements to select a bra, then try it on. Check that the band is level and snug, the cups are smooth, and the straps don't dig in. Checkpoint: The center gore should lie flat against your sternum without gaping.

Bras That Fit Small Busts Well

• Elodie: Elodie is a deep-plunge bra hidden beneath a full-coverage lace bralette. Molded cups and interior mesh panels create light shape and lift without added padding or an underwire. This is ideal if you want a smooth, natural silhouette without extra bulk—perfect for everyday wear when you've measured your size and want a comfortable, supportive fit.
• Hattie: Hattie combines the comfort of a bralette with enough coverage to create natural shape and cleavage. It features soft, satiny microfiber for a smooth silhouette and a deep-plunge neckline. If you have close-set breasts, Hattie's deep plunge and soft fabric can help avoid gaping while providing a flattering shape that feels like a bralette.
• Courtney: Courtney is a demi-cup bra designed to create a sculpted silhouette and boosted bustline. Removable push-up pads let you customize the shape and lift of each cup. This is a great option if you want to adjust the fit after measuring, especially if one breast is slightly larger—you can add or remove padding to balance the look.