Bra Atlas

34DD sister sizes, conversions and measurements

34DD was the most common self-reported size in a UK study that compared the traditional method with professional fitting, and that study found the old method oversized bands and undersized cups.

Bra Atlas fitting card

34DDUK · same in the US

Measures about 34 in underbust and 39 in bust. Same cups as 32E and 36D.

UK
34DD
US
34DD
EU
75E
FR
90E
AU
12DD
JP
F75

Same cups 32E34DD36D

Every sister of 34DD

  • 28FFTighter band by 6 in, 3 cup letters up (US 28H, EU 60H)
  • 30FTighter band by 4 in, 2 cup letters up (US 30G, EU 65G)
  • 32ETighter band by 2 in, 1 cup letter up (US 32DDD, EU 70F)
  • 34DDThis size (US 34DD, EU 75E)
  • 36DLooser band by 2 in, 1 cup letter down (US 36D, EU 80D)
  • 38CLooser band by 4 in, 2 cup letters down (US 38C, EU 85C)
  • 40BLooser band by 6 in, 3 cup letters down (US 40B, EU 90B)

By Rai Ansar · Sizes computed by the Bra Atlas engine, sources checked · How this page was made

32E: band 32 in, same cup volume

32E

tighter band

34DD: band 34 in, same cup volume

34DD

your size

36D: band 36 in, same cup volume

36D

looser band

Same cups, three bands: 32E, 34DD, 36D hold the same cup volume.

Tape measurements that give 34DD

Computed by the Bra Atlas engine with the measured-band method, and checked by running each pair back through it.

Underbust and bust for 34DDA bust within about a quarter inch of the figure shown still gives 34DD.
Snug underbustFullest bustResult
33 in (84 cm)38.5 in (98 cm)34DD
33.5 in (85 cm)38.75 in (98 cm)34DD
34 in (86 cm)39 in (99 cm)34DD
34.5 in (88 cm)39.25 in (100 cm)34DD

Same body, other methods: 34 in and 39 in is a 38A with the traditional +4 method. With an odd 33 in underbust and a 38.5 in bust we print 34DD; calculator.net's rule (band rounded, cup from the raw difference) would print 34E. Why methods differ.

What is particular about 34DD

"34dd sister size" gets about 1,000 Google searches a month in the US and 90 in the UK (Google Ads data, September 2026).

The size a UK study kept finding

White and Scurr (Ergonomics, 2012) recruited 45 women in the UK; the size they most often reported wearing was 34DD. Measured with the traditional method, the group's bands came out too big and cups too small compared with professional fitting criteria. If you have worn 34DD for years, measure again with the measured-band method before you buy.

Where the labels split

34DD is the same on UK and US labels, but its tighter sister is not: UK 32E, US 32DDD. That is where most sister-size charts that only print US letters mislead UK shoppers.

What the +4 method does to this body

A 34 in underbust and a 39 in bust measure 34DD. The +4 method gives 38A: the band padded by 4 in, the cup from 39 − 38 = 1 in.

34DD in every system

34DD and its sisters on six labelsEach row holds the same cup volume.
UKUSEUFRAUJP (approx.)
28FF28H60H75H6GI60
30F30G65G80G8FH65
32E32DDD70F85F10EG70
34DD34DD75E90E12DDF75
36D36D80D95D14DE80
38C38C85C100C16CD85
40B40B90B105B18BC90

Other sizes and tools

Sources

Each source was opened and checked on 25 September 2026. Where sources disagree, the page says so instead of picking one silently.

  1. White J, Scurr J. Evaluation of professional bra fitting criteria for bra selection and fitting in the UK. Ergonomics 2012;55(6):704-711: 45 women; the traditional method overestimated band and underestimated cup
  2. Wikipedia, "Bra size": UK and US cup ladders, the +4 method, EN 13402 and JIS cup steps
  3. A Bra That Fits calculator (community calculator of r/ABraThatFits): we submitted 18 measurement pairs in 6 systems on 25 September 2026; raw output is in our repository