Petite Bra Sizes Explained: AA, AAA, and Finding Your Fit

If you're just starting to develop, or you've never quite found a size that felt right, here's what's actually true about petite bra sizes — and how to find yours accurately.

What's the Smallest Bra Size?

The smallest commonly available bra size is typically 28AA, though AAA sizes exist too. A 28AA means the bust measurement is less than an inch larger than the band measurement — a real, if less common, proportion.

Is A the Smallest Cup Size?

A is often the smallest size available at major retailers, but it isn't the smallest cup size that exists. Brands that carry a fuller size range, like BRABAR, also offer AA and AAA. If you can't find your size, an in-person fitting can help confirm it.

A isn't automatically the right size either — cup capacity is relative to band size, so the right cup letter depends on both measurements together, not cup letter alone.

How Band and Cup Size Work Together

Band and cup size move together: going down a band size generally means going up a cup letter to preserve the same cup volume, and going up a band size means going down a cup letter. The band does the actual supporting work, so getting that measurement right — not too loose, not too tight — matters most. See BRABAR's Sister Sizing Explained for the full mechanics.

What Counts as a Small Cup Size?

Cup size is the difference between bust and band measurement, in inches. Generally, AAA through C are considered smaller cup sizes — a difference of about 0.5 to 3 inches between bust and band.

If you've measured out at exactly AA and want to know more about that specific size, from why it's hard to find in stores to what actually changes with an accurate fit, see BRABAR's Being an AA Cup.

Shopping for Petite Sizes

BRABAR's Everyday Bra works well under everything, for daily wear. The Soft Strapless Bra Top, with its sweetheart neckline, works well under a jacket or an evening dress. The cami bra tops make good everyday or lounge options, and halter styles — like the HUG Lace Halter Bralette — work well for sloping shoulders where straps tend to slip, and pair nicely under a range of necklines.

Find your accurate size with BRABAR's Fit Guide and Bra Size Calculator, or explore the AA-C cup collection.

Frequently Asked Questions

What is the smallest common bra size?

28AA is the smallest commonly available size, though AAA sizes exist. A 28AA means the bust measurement is less than an inch larger than the band.

Is A always the smallest cup size?

No. A is often the smallest size at major retailers, but AA and AAA exist and are real, common proportions at brands that stock a fuller range.

How does band size affect cup size?

Cup capacity is relative to band size. Going down a band size generally means going up a cup letter to keep the same cup volume, and vice versa.