28AA Bra Size
28AA fits a 27–29 inch (69–74 cm) underbust and a full bust of about 29 inches (74 cm).
Last reviewed on 25 September 2026.
28AA at a glance
| Underbust (band) | 27–29 in · 69–74 cm |
|---|---|
| Full bust | ≈ 29 in · 74 cm |
| Bust minus underbust | ≈ 1 in · 3 cm |
| Sister sizes (same cup volume) | — |
| UK / EU / FR / AU | 28AA · 60AA · 75AA · 6AA |
| One cup bigger | 28A |
| Approx. top size | XXS–XS · UK 4–6 / US 0–2 |
Measurements for 28AA
28AA is built for an underbust ribcage measurement that falls in the 27–29 inch range, with a full-bust measurement around 29 inches. The band number — 28 — is a smaller band that needs to sit firmly without cutting in. The cup letter — AA — describes the difference between the two measurements; an AA cup means the full bust is only about one inch larger than the underbust — there is little projection, and the cup mostly serves as smooth coverage rather than tissue support.
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28AA in Other Sizing Systems
EU, FR, and JP sizing read the band in centimetres, which is why 28AA maps to 60AA (EU), 75AA (FR), and 60AA (JP) — the same body, expressed in different units. AU sizing uses a small numeric scale (6AA for this band). UK sizing shares the band number with the US but parts ways at the cup once you go past D, so 28AA reads as 28AA on a UK label.
Sister Sizes for 28AA
These sizes have the same cup volume as 28AA. Try them if the band feels too tight or too loose.
← Tighter band, bigger cup · Looser band, smaller cup →
Sister sizes are useful when the cup of your 28AA fits well but the band is wrong — too loose by the end of the day, or too tight to clip up comfortably. Going one band smaller and one cup larger keeps the cup volume the same while tightening the band; going the other way loosens the band without losing cup space. Read the full sister-size matrix if you want to see how this works for every size at once.
Fit Tips for 28AA
AA cups can be hard to find in mainstream stores. Brands and ranges focused on petite or smaller-cup fitting tend to carry more options, often in soft-cup, bralette, or triangle styles.
If your 28AA bra is gapping at the top of the cup, the cup may be too large or the wrong shape — try a demi-cup or balconette before assuming the size is wrong. If the centre piece between the cups (the gore) does not lay flat against your sternum, the cup is almost certainly too small; go up one cup. If the band rides up across your back during the day, the band has stretched out or was too loose to begin with — drop one band size and add one cup to keep the same cup volume.
For more detailed troubleshooting, the Fit Test on the home page covers six common visible problems and the size or shape change that usually addresses each one. The guide to measuring mistakes covers the most common reasons a calculation comes out wrong in the first place.
Related sizes
If 28AA is close but not quite right, these neighbouring sizes are the most useful next places to look:
See every size at a glance on the full bra size index, or read how to measure your bra size if you are not sure 28AA is right for you.
28AA — frequently asked questions
What measurements are a 28AA bra in inches and cm?
A 28AA bra fits an underbust (ribcage) measurement of roughly 27 to 29 inches (69–74 cm) and a full-bust measurement of about 29 inches (74 cm). The cup letter AA reflects the roughly 1-inch (3 cm) difference between those two numbers.
What size is equivalent to 28AA? (sister sizes)
28AA sits at the edge of the standard size range, so it has only a partial set of sister sizes. The general rule still holds: to tighten the band, drop one band size and add one cup; to loosen it, add one band size and drop one cup.
What is 28AA in UK, EU, and other sizing systems?
28AA (US) converts to 28AA in UK sizing, 60AA in EU sizing, 75AA in French sizing, 6AA in Australian sizing, and 60AA in Japanese sizing. The body is the same; only the labelling system changes.
Is 28AA a small or large bra size?
In terms of how common it is, this size pairs a small band with a smaller cup. There is no universal "small" or "large" bra size — the same cup letter describes a different volume on every band — but within the full range BraCalc covers (bands 28–48, cups AA–H) this combination sits toward the compact end.
Is 28AA a small, medium, large, or XL?
As a rough guide, a 28 band usually matches size XXS–XS in tops and bralettes — around UK dress size 4–6 (US 0–2). The band number drives this more than the cup letter, so 28AA lands in the same letter size as other 28-band bras. Letter sizing varies a lot between brands, so always check the brand's own chart.
What is the next size up or down from 28AA?
Keeping the same 28 band, one size up in the cup is 28A. If you want a bigger or smaller band but the same cup volume, use a sister size instead: drop one band and add one cup, or the reverse. Remember that the cup letter is relative to the band — 30AA has more cup volume than 28AA, not the same.
Not sure about your size? Measure yourself and double-check.
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