Short answer: 36C holds more volume than 34C. But it's not that simple — because band size changes everything. Here's what you need to know.

The Numbers Explained

Bra sizes are two numbers working together:

  • 34 or 36 = your band size (ribcage measurement)
  • C = your cup size (difference between bust and band)

A C cup means your bust is about 3 inches larger than your band. So 34C means a 34-inch band with a 37-inch bust. 36C means a 36-inch band with a 39-inch bust. The bust is physically larger in 36C.

But What About Sister Sizes?

Here's where it gets interesting. 34C and 36C are not sister sizes. They have different cup volumes. The actual sister sizes are:

  • 34C → sister to 36B (same cup volume, looser band)
  • 36C → sister to 34D (same cup volume, tighter band)

So 34C and 36B hold the same breast volume, while 36C holds more. And 36C and 34D hold the same volume. If your 34C band feels tight but the cups fit, try 36B. If the cups feel small but the band fits, try 34D.

Which One Should You Wear?

It depends on your measurements. If your underbust is around 34 inches, you need a 34 band. If it's 36 inches, you need a 36 band. Don't choose a band size to get a bigger cup — that leads to a poor fit.

Not sure about your measurements? Use our Bra Size Calculator to find your exact size, then check how it converts across countries and brands.

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