What is B Cup Size? B Cup Bra Measurements in Inches & cm, 30B to 40B

In bra sizing, a B cup means your bust measures about 2 inches (5 cm) more than your band size. So "B cup" is not one fixed size: a 32B has a bust of about 34 inches and a 38B a bust of about 40 inches, because the cup letter only describes the difference between bust and band. B is the most common cup size in India. Below is every B cup size from 30B to 40B with its measurements in inches and cm, how to check you are a B cup, which sizes hold the same cup volume, and which bra styles suit a B cup.

B cup size chart: 30B to 40B

Size	Underbust (inches)	Bust (inches)	Bust (cm)	Shop
30B	25–26	32	81	30B bras
32B	27–28	34	86	32B bras
34B	29–30	36	91	34B bras
36B	31–32	38	97	36B bras
38B	33–34	40	102	38B bras
40B	35–36	42	107	40B bras

Every row is a B cup, but the cups are not the same size: cup volume grows with the band, so a 38B cup holds noticeably more than a 32B cup. The band number is your underbust plus 4 (even) or 5 (odd) inches; the cup letter is bust minus band, where A is 1 inch, B is 2, C is 3, D is 4 and E is 5.

How to know if you are a B cup

Measure under your bust, snug, in inches, and convert to a band: add 4 if the number is even, 5 if it is odd.
Measure around the fullest part of your bust, loosely, without pressing.
Subtract the band from the bust. A difference of 2 inches is a B cup; 1 is A; 3 is C.

Example: underbust 29 inches gives band 34; bust 36 inches is 36 minus 34 = 2, so 34B. Use the bra size chart for every band or the bra size calculator to do the maths.

Is B cup big or small?

In India, B is the most common cup: 32B, 34B and 36B are the three best-selling bra sizes on Lovable India and on most Indian sites. On its own, the letter says little about how a bust looks: a B cup on a 30 band is small, a B cup on a 40 band is full. B cup is one letter larger than A and one smaller than C: each letter adds one inch to the bust-minus-band difference.

B cup sister sizes

Sister sizes share the same cup volume on a different band. If your B cup bra fits in the cup but the band is tight, go up a band and down a cup; if the band rides up, go down a band and up a cup.

B cup size	Same cup, tighter band	Same cup, looser band
30B	–	32A
32B	30C	34A
34B	32C	36A
36B	34C	38A
38B	36C	40A
40B	38C	–

Best bra styles for B cups

B cups suit almost every style. Lightly padded and push-up bras add shape under fitted tops; t-shirt and seamless bras disappear under thin fabrics; non-padded cotton bras are the coolest daily option; non-wired works fine because the cup is light. Browse t-shirt bras, padded bras, non-padded bras, seamless bras, sports bras and full coverage bras, then filter to your B cup size.

B cup FAQs

What does B cup mean?

That your bust is about 2 inches (5 cm) larger than your band size. It is a difference, not a measurement, so the actual cup size depends on the band: 32B, 34B and 36B are all B cups of different sizes.

What is B cup size in cm?

The difference between bust and band is about 5 cm. In centimetres the full sizes are: 32B bust 86 cm, 34B bust 91 cm, 36B bust 97 cm, 38B bust 102 cm.

What is the difference between A cup and B cup?

One inch. An A cup is a bust 1 inch larger than the band; a B cup is 2 inches larger. On a 34 band that is a bust of 35 inches (34A) versus 36 inches (34B).

Which B cup size is most common in India?

34B, which is also the single most common bra size in India, followed by 32B and 36B.

Is a B cup the same on every band?

No. Cup volume increases with the band, so 36B holds more than 34B, which holds more than 32B. The size with the same cup volume as 34B is 32C on a tighter band and 36A on a looser band.

Which bra is best for a B cup?

A lightly padded t-shirt bra for daily wear and a non-padded cotton bra for home; almost every style fits a B cup. See all bras on Lovable India from ₹179 and filter to your B cup size.

More bra size guides

Bra Size Chart | Bra Size Calculator | What A, B, C, D Cup Sizes Mean

By band: 30 Bra Size | 32 Bra Size | 34 Bra Size | 36 Bra Size | 38 Bra Size

By size: 30B | 32B | 32C | 32D | 34B | 34C | 34D | 36B | 36C | 36D | 38B | 38C | 38D

By cup: A Cup | C Cup | D Cup

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