34DDD Bra Size
34DDD fits a 33–35 inch (84–89 cm) underbust and a full bust of about 41 inches (104 cm). Its sister sizes are 32G and 36DD.
Last reviewed on 25 September 2026.
34DDD at a glance
| Underbust (band) | 33–35 in · 84–89 cm |
|---|---|
| Full bust | ≈ 41 in · 104 cm |
| Bust minus underbust | ≈ 7 in · 18 cm |
| Sister sizes (same cup volume) | 32G · 36DD |
| UK / EU / FR / AU | 34E · 75F · 90F · 12E |
| Same size in US | 34F |
| One cup bigger | 34G |
| One cup smaller | 34DD |
| Approx. top size | M · UK 10–12 / US 6–8 |
Measurements for 34DDD
34DDD is built for an underbust ribcage measurement that falls in the 33–35 inch range, with a full-bust measurement around 41 inches. The band number — 34 — is one of the most widely produced band sizes, with broad style choice. The cup letter — DDD — describes the difference between the two measurements; a DDD cup (US) means the full bust is about seven inches larger than the underbust — this is where US notation diverges from UK, where the same volume is called an E cup. Many US labels print it as DDD/F.
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34DDD in Other Sizing Systems
EU, FR, and JP sizing read the band in centimetres, which is why 34DDD maps to 75F (EU), 90F (FR), and 75F (JP) — the same body, expressed in different units. AU sizing uses a small numeric scale (12E for this band). UK sizing shares the band number with the US but parts ways at the cup once you go past D, so 34DDD reads as 34E on a UK label.
Is 34DDD the same as 34F or 34E? In US sizing, yes to 34F: the cup letters go AA, A, B, C, D, DD, DDD, then G, and many US retailers print this cup as "DDD/F" — 34F and 34DDD are the same size. In UK sizing the same cup is called 34E, and in EU sizing it is 34F with a centimetre band. A UK 34F is one cup bigger — it matches a US 34G.
Sister Sizes for 34DDD
These sizes have the same cup volume as 34DDD. 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 34DDD 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 34DDD
DDD (often labelled DDD/F in US sizing) benefits from full-coverage cups and three-part construction that offers more structure. Side support panels help redirect tissue forward and reduce side spillage.
If your 34DDD 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 34DDD 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 34DDD is right for you.
34DDD — frequently asked questions
What measurements are a 34DDD bra in inches and cm?
A 34DDD bra fits an underbust (ribcage) measurement of roughly 33 to 35 inches (84–89 cm) and a full-bust measurement of about 41 inches (104 cm). The cup letter DDD reflects the roughly 7-inch (18 cm) difference between those two numbers.
What size is equivalent to 34DDD? (sister sizes)
The sister sizes of 34DDD are 32G (tighter band, one cup letter up) and 36DD (looser band, one cup letter down). They hold the same cup volume as 34DDD on a different band. Try a sister size when the cups of your 34DDD fit but the band feels too loose or too tight.
What is 34DDD in UK, EU, and other sizing systems?
34DDD (US) converts to 34E in UK sizing, 75F in EU sizing, 90F in French sizing, 12E in Australian sizing, and 75F in Japanese sizing. The body is the same; only the labelling system changes.
Is 34DDD a small or large bra size?
In terms of how common it is, this size pairs an average band with a fuller-bust 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 fuller end.
Is 34DDD 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 34DDD lands in the same letter size as other 34-band bras. With a fuller cup, many people go one size up in fitted tops so the bust has room. Letter sizing varies a lot between brands, so always check the brand's own chart.
What is the next size up or down from 34DDD?
Keeping the same 34 band, one size up in the cup is 34G, and one size down is 34DD. If you want a bigger or smaller band but the same cup volume, use a sister size instead: 32G or 36DD. Remember that the cup letter is relative to the band — 36DDD has more cup volume than 34DDD, not the same.
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