38AA Bra Size
38AA fits a 37–39 inch (94–99 cm) underbust and a full bust of about 39 inches (99 cm). Its sister sizes are 36A.
Last reviewed on 25 September 2026.
38AA at a glance
| Underbust (band) | 37–39 in · 94–99 cm |
|---|---|
| Full bust | ≈ 39 in · 99 cm |
| Bust minus underbust | ≈ 1 in · 3 cm |
| Sister sizes (same cup volume) | 36A |
| UK / EU / FR / AU | 38AA · 85AA · 100AA · 16AA |
| One cup bigger | 38A |
| Approx. top size | L–XL · UK 14–16 / US 10–12 |
Measurements for 38AA
38AA is built for an underbust ribcage measurement that falls in the 37–39 inch range, with a full-bust measurement around 39 inches. The band number — 38 — is a mid-range band where the most common fit issue is the band riding up because it has stretched. 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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38AA in Other Sizing Systems
EU, FR, and JP sizing read the band in centimetres, which is why 38AA maps to 85AA (EU), 100AA (FR), and 85AA (JP) — the same body, expressed in different units. AU sizing uses a small numeric scale (16AA for this band). UK sizing shares the band number with the US but parts ways at the cup once you go past D, so 38AA reads as 38AA on a UK label.
Sister Sizes for 38AA
These sizes have the same cup volume as 38AA. 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 38AA 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 38AA
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 38AA 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 38AA 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 38AA is right for you.
38AA — frequently asked questions
What measurements are a 38AA bra in inches and cm?
A 38AA bra fits an underbust (ribcage) measurement of roughly 37 to 39 inches (94–99 cm) and a full-bust measurement of about 39 inches (99 cm). The cup letter AA reflects the roughly 1-inch (3 cm) difference between those two numbers.
What size is equivalent to 38AA? (sister sizes)
The sister sizes of 38AA are 36A (tighter band, one cup letter up). They hold the same cup volume as 38AA on a different band. Try a sister size when the cups of your 38AA fit but the band feels too loose or too tight.
What is 38AA in UK, EU, and other sizing systems?
38AA (US) converts to 38AA in UK sizing, 85AA in EU sizing, 100AA in French sizing, 16AA in Australian sizing, and 85AA in Japanese sizing. The body is the same; only the labelling system changes.
Is 38AA a small or large bra size?
In terms of how common it is, this size pairs an above-average 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 38AA a small, medium, large, or XL?
As a rough guide, a 38 band usually matches size L–XL in tops and bralettes — around UK dress size 14–16 (US 10–12). The band number drives this more than the cup letter, so 38AA lands in the same letter size as other 38-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 38AA?
Keeping the same 38 band, one size up in the cup is 38A. If you want a bigger or smaller band but the same cup volume, use a sister size instead: 36A. Remember that the cup letter is relative to the band — 40AA has more cup volume than 38AA, not the same.
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