B Cup Size Guide
B cup represents a 2-inch difference between bust and band measurements. It's a small-medium cup size that offers versatility in bra style options.
Quick Facts: B Cup
Bust-Band Difference
2 inches (5 cm)
Approx. Volume (34 band)
~200-250 ml
UK Equivalent
B
EU Equivalent
B
Common B Cup Sizes
B Cup Works Best For
- ✓Slim to average frames
- ✓Active lifestyles
- ✓Natural shape emphasis
- ✓Versatile wardrobe needs
Common Challenges
- !May fall between sizes in some brands
- !Some styles may not provide enough shape
Best Bra Styles for B Cup
Sister Sizes for B Cup
Sister sizes have the same cup volume with different band sizes. If your band feels too tight or loose, try a sister size.
Tighter Band
30C
Your Size
34B
Looser Band
34A
Frequently Asked Questions: B Cup
Is a B cup a common size?
Yes, B cup is one of the most commonly purchased bra sizes, though studies suggest many B cup wearers may actually need a different size.
What's the difference between B and C cup?
A C cup has about 1 inch more bust projection than a B cup. The difference is noticeable but subtle, which is why sister sizing works well between these sizes.
Do B cups need underwire?
Not necessarily. B cups have enough support needs that underwire can help with shape, but many find wireless options comfortable and supportive enough.
Find Your Perfect B Cup Bra
Use our calculator to confirm your size and get personalized recommendations.