Bra Atlas

34C sister sizes, conversions and measurements

34C is behind the most searched size query we measured ("34c bra size", 9,900 a month in the US), and it is the size brands reach for when they explain sister sizing.

Bra Atlas fitting card

34CUK · same in the US

Measures about 34 in underbust and 37 in bust. Same cups as 32D and 36B.

UK
34C
US
34C
EU
75C
FR
90C
AU
12C
JP
D75

Same cups 32D34C36B

Every sister of 34C

  • 28ETighter band by 6 in, 3 cup letters up (US 28DDD, EU 60F)
  • 30DDTighter band by 4 in, 2 cup letters up (US 30DD, EU 65E)
  • 32DTighter band by 2 in, 1 cup letter up (US 32D, EU 70D)
  • 34CThis size (US 34C, EU 75C)
  • 36BLooser band by 2 in, 1 cup letter down (US 36B, EU 80B)
  • 38ALooser band by 4 in, 2 cup letters down (US 38A, EU 85A)
  • 40AALooser band by 6 in, 3 cup letters down (US 40AA, EU 90AA)

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

32D: band 32 in, same cup volume

32D

tighter band

34C: band 34 in, same cup volume

34C

your size

36B: band 36 in, same cup volume

36B

looser band

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

Tape measurements that give 34C

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

Underbust and bust for 34CA bust within about a quarter inch of the figure shown still gives 34C.
Snug underbustFullest bustResult
33 in (84 cm)36.5 in (93 cm)34C
33.5 in (85 cm)36.75 in (93 cm)34C
34 in (86 cm)37 in (94 cm)34C
34.5 in (88 cm)37.25 in (95 cm)34C

Same body, other methods: 34 in and 37 in is a 38 (below AA) with the traditional +4 method. With an odd 33 in underbust and a 36.5 in bust we print 34C; calculator.net's rule (band rounded, cup from the raw difference) would print 34D. Why methods differ.

What is particular about 34C

"34c sister size" gets about 2,400 Google searches a month in the US and 320 in the UK (Google Ads data, September 2026).

The example brands use

Marks & Spencer and Victoria's Secret UK both explain sister sizes with 34C: the same cup volume as 32D and 36B. Our chart draws the same line, and on to 30DD and 38A.

M&S's US chart calls it 34B

On the Marks & Spencer US size guide, a UK 34C is listed as US 34B (bands 30 and 34 to 46 shift one letter; 28 and 32 do not). Wacoal, Freya and Victoria's Secret all print UK 34C = US 34C, and so do we. Shopping M&S from the US, go by the UK label.

What the +4 method does to this body

A 34 in underbust and a 37 in bust measure 34C. The +4 method pads the band to 38, which is more than the 37 in bust, so it has no cup letter to give at all. That is the padded band at its most confusing.

34C in every system

34C and its sisters on six labelsEach row holds the same cup volume.
UKUSEUFRAUJP (approx.)
28E28DDD60F75F6EG60
30DD30DD65E80E8DDF65
32D32D70D85D10DE70
34C34C75C90C12CD75
36B36B80B95B14BC80
38A38A85A100A16AB85
40AA40AA90AA105AA18AAA90

Other sizes and tools

Sources

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

  1. Marks & Spencer, "How to Measure Bra Size": fit checks; sister sizing; a tape gives a rough starting point (opened 26 September 2026)
  2. Marks & Spencer US, "Bras size guide": UK, AU/NZ, US/CA, EU and FR conversion table (opened 26 September 2026)
  3. Victoria's Secret UK, "Measure Your Bra Size": band = snug underbust rounded to the nearest even number; fit fixes; sister table (opened 26 September 2026)
  4. Wikipedia, "Bra size": UK and US cup ladders, the +4 method, EN 13402 and JIS cup steps