Bra Atlas fitting card
34BUK · same in the US
Measures about 34 in underbust and 36 in bust. Same cups as 32C and 36A.
- UK
- 34B
- US
- 34B
- EU
- 75B
- FR
- 90B
- AU
- 12B
- JP
- C75
Same cups 32C·34B·36A
34B sister sizes, conversions and measurements
"34b bra size" gets 9,900 US searches a month, more than any other size we measured, and 34B is where the traditional +4 method fails outright: it cannot return a cup letter at all.
Every sister of 34B
- 28DDTighter band by 6 in, 3 cup letters up (US 28DD, EU 60E)
- 30DTighter band by 4 in, 2 cup letters up (US 30D, EU 65D)
- 32CTighter band by 2 in, 1 cup letter up (US 32C, EU 70C)
- 34BThis size (US 34B, EU 75B)
- 36ALooser band by 2 in, 1 cup letter down (US 36A, EU 80A)
- 38AALooser band by 4 in, 2 cup letters down (US 38AA, EU 85AA)
32C
tighter band
34B
your size
36A
looser band
Same cups, three bands: 32C, 34B, 36A hold the same cup volume.
Tape measurements that give 34B
Computed by the Bra Atlas engine with the measured-band method, and checked by running each pair back through it.
| Snug underbust | Fullest bust | Result |
|---|---|---|
| 33 in (84 cm) | 35.5 in (90 cm) | 34B |
| 33.5 in (85 cm) | 35.75 in (91 cm) | 34B |
| 34 in (86 cm) | 36 in (91 cm) | 34B |
| 34.5 in (88 cm) | 36.25 in (92 cm) | 34B |
Same body, other methods: 34 in and 36 in is a 38 (below AA) with the traditional +4 method. With an odd 33 in underbust and a 35.5 in bust we print 34B; calculator.net's rule (band rounded, cup from the raw difference) would print 34C. Why methods differ.
What is particular about 34B
"34b sister size" gets about 1,000 Google searches a month in the US and 140 in the UK (Google Ads data, September 2026).
Where the +4 method runs out
A 34 in underbust and a 36 in bust measure 34B on the measured-band method. The +4 method pads the band to 38 in, two inches more than the bust itself, and prints "38 (below AA)": the cup difference goes negative and it has no letter to give. That is the padded band failing completely, not just rounding a size away.
A small step either way
If a 34B band rides up, 32C is one band tighter with the same cups. If it digs in, 36A is one band looser. Both keep the cup volume of 34B.
The same in the UK and US
34B reads the same on UK and US labels, and so do its sisters at this end of the chart: 32C, 36A, 38AA. The letters only split once you reach DD.
34B in every system
| UK | US | EU | FR | AU | JP (approx.) |
|---|---|---|---|---|---|
| 28DD | 28DD | 60E | 75E | 6DD | F60 |
| 30D | 30D | 65D | 80D | 8D | E65 |
| 32C | 32C | 70C | 85C | 10C | D70 |
| 34B | 34B | 75B | 90B | 12B | C75 |
| 36A | 36A | 80A | 95A | 14A | B80 |
| 38AA | 38AA | 85AA | 100AA | 16AA | A85 |
Other sizes and tools
- Bra size calculatorCheck that 34B is still your size, with both methods shown
- Sister size chartThe full diagonal chart and fit fixes
- Fit checkTick what feels wrong in your 34B; get the size to try next
- Brand size chartsHow Victoria's Secret, ThirdLove, Wacoal, SKIMS, M&S and Freya label 34B
- B cup, explainedWhat the B cup means, and why it changes by band
- 30DSister sizes, conversions and measurements
- 32DDSister sizes, conversions and measurements
- 34CSister sizes, conversions and measurements
- 34DSister sizes, conversions and measurements
- 34DDSister sizes, conversions and measurements
- 36CSister sizes, conversions and measurements
- 36DDSister sizes, conversions and measurements
- 38DSister sizes, conversions and measurements
Sources
Each source was opened and checked on 25 September 2026. Where sources disagree, the page says so instead of picking one silently.
- Wikipedia, "Bra size": UK and US cup ladders, the +4 method, EN 13402 and JIS cup steps
- 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