Two numbers and a bit of arithmetic. The band is a measurement; the cup is a difference — and almost everything that goes wrong goes wrong in the band.
A bra size is not one size, it is two facts stuck together. The number is your underbust measurement, converted into whatever ladder the country uses. The letter is the difference between your bust and your underbust — not a volume, not a size, a gap. That is why the same letter means a different cup on a different band.
Take the two measurements
Wear a soft, unpadded bra, or none. A padded one adds its own volume to the bust measurement.
Underbust: run the tape directly under the bust, level all the way around and snug — this one is meant to be firm.
Bust: around the fullest part, tape level, standing upright and not holding your breath.
Write both down in centimetres, and subtract the underbust from the bust. That difference is your cup.
Underbust → band size
Women's — Bra Band by Underbust circumference
cmUnderbust circumference
inUnderbust circumference
USUnited States
EUEurope
UKUnited Kingdom
JPJapan
KRKorea
CNChina
63
24.8
28
65
28
60
60
60
68
26.8
30
70
30
65
65
65
73
28.7
32
75
32
70
70
70
78
30.7
34
80
34
75
75
75
83
32.7
36
85
36
80
80
80
88
34.6
38
90
38
85
85
85
93
36.6
40
95
40
90
90
90
98
38.6
42
100
42
95
95
95
The European, Japanese, Korean and Chinese bands are centimetre figures, which is why they look nothing like the US and UK inch numbers. A US 34 band and a EU 80 band are the same bra.
Bust minus underbust → cup size
Cup size from the difference between bust and underbust
cmBust − underbust
inBust − underbust
USUnited States
EUEurope
UKUnited Kingdom
JPJapan
KRKorea
CNChina
up to 9
up to 3.5
AA
AA
AA
AA
AA
AA
9.5–12
3.7–4.7
A
A
A
A
A
A
12.5–14
4.9–5.5
B
B
B
B
B
B
14.5–16
5.7–6.3
C
C
C
C
C
C
16.5–18
6.5–7.1
D
D
D
D
D
D
18.5–20
7.3–7.9
DD
E
DD
E
E
E
20.5–22
8.1–8.7
DDD
F
E
F
F
F
22.5 and over
8.9 and over
DDDD
G
F
G
G
G
Above a D the letters stop agreeing with each other. Some brands and countries go D, DD, DDD; others go D, E, F; some European labels use yet another ladder. The measurement underneath is identical — only the alphabet changes — so above a D always check the brand's own chart rather than trusting the letter.
If it does not feel right
The band rides up your back. It is too big. The band carries most of the support, so this is the one to fix first — go down a band, and up a cup to keep the same volume.
The straps dig in. Usually the same problem: the band is not doing its job, so the straps are.
The centre panel does not lie flat. The cup is too small, whatever the letter says.
It fitted last year. Bodies change, and bras wear out — the elastic in a band that is worn constantly gives up long before the fabric does.
Common questions
What is a EU 75 bra band in US sizes?
A US 32. The European number is the underbust in centimetres; the US number is the same measurement on an inch-based ladder.
Should I measure with a bra on?
Wear a soft, unpadded bra or nothing at all. A padded bra adds its own volume and inflates the bust measurement, which pushes you a full cup out.
Why does the same size fit differently in two shops?
Because cup letters above D are labelled differently from brand to brand and country to country, and because band elastic and cup shape vary hugely. The measurements are the constant; the letters are not.
How do I convert a UK bra size to EU?
Band and cup convert separately. Look the band up in the bra band chart and the cup in the bra cup chart — a UK 34 band is a EU 80.
The charts behind this
More guides
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