34A Bra Size
34A fits a 33–35 inch (84–89 cm) underbust and a full bust of about 36 inches (91 cm). Its sister sizes are 32B and 36AA.
Last reviewed on 25 September 2026.
34A at a glance
| Underbust (band) | 33–35 in · 84–89 cm |
|---|---|
| Full bust | ≈ 36 in · 91 cm |
| Bust minus underbust | ≈ 2 in · 5 cm |
| Sister sizes (same cup volume) | 32B · 36AA |
| UK / EU / FR / AU | 34A · 75A · 90A · 12A |
| One cup bigger | 34B |
| One cup smaller | 34AA |
| Approx. top size | M · UK 10–12 / US 6–8 |
Measurements for 34A
34A is built for an underbust ribcage measurement that falls in the 33–35 inch range, with a full-bust measurement around 36 inches. The band number — 34 — is one of the most widely produced band sizes, with broad style choice. The cup letter — A — describes the difference between the two measurements; an A cup means the full bust is about two inches larger than the underbust — light shaping and bralette styles are common at this size.
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34A in Other Sizing Systems
EU, FR, and JP sizing read the band in centimetres, which is why 34A maps to 75A (EU), 90A (FR), and 75A (JP) — the same body, expressed in different units. AU sizing uses a small numeric scale (12A for this band). UK sizing shares the band number with the US but parts ways at the cup once you go past D, so 34A reads as 34A on a UK label.
Sister Sizes for 34A
These sizes have the same cup volume as 34A. 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 34A 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 34A
A-cup bras often benefit from light padding for shape, though many wearers prefer unpadded cups. Bralettes and triangle styles are common and comfortable for everyday wear.
If your 34A 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 34A 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 34A is right for you.
34A — frequently asked questions
What measurements are a 34A bra in inches and cm?
A 34A bra fits an underbust (ribcage) measurement of roughly 33 to 35 inches (84–89 cm) and a full-bust measurement of about 36 inches (91 cm). The cup letter A reflects the roughly 2-inch (5 cm) difference between those two numbers.
What size is equivalent to 34A? (sister sizes)
The sister sizes of 34A are 32B (tighter band, one cup letter up) and 36AA (looser band, one cup letter down). They hold the same cup volume as 34A on a different band. Try a sister size when the cups of your 34A fit but the band feels too loose or too tight.
What is 34A in UK, EU, and other sizing systems?
34A (US) converts to 34A in UK sizing, 75A in EU sizing, 90A in French sizing, 12A in Australian sizing, and 75A in Japanese sizing. The body is the same; only the labelling system changes.
Is 34A a small or large bra size?
In terms of how common it is, this size pairs an 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 34A a small, medium, large, or XL?
As a rough guide, a 34 band usually matches size M in tops and bralettes — around UK dress size 10–12 (US 6–8). The band number drives this more than the cup letter, so 34A lands in the same letter size as other 34-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 34A?
Keeping the same 34 band, one size up in the cup is 34B, and one size down is 34AA. If you want a bigger or smaller band but the same cup volume, use a sister size instead: 32B or 36AA. Remember that the cup letter is relative to the band — 36A has more cup volume than 34A, not the same.
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