34B vs 34C | What’s Actually Different?

If you’re comparing a 34B to a 34C, the band number 34 is identical. That means both bras are built for the same underbust measurement, roughly 30–31 inches. The only thing that changes is the cup.

The cup difference

Cup letters measure the gap between your bust (fullest point) and your band. A B cup means about a 2-inch difference; a C cup means about a 3-inch difference. So a 34C simply holds one inch more volume than a 34B, on the same band.

Which one should you choose?

• If your current 34B feels tight across the cups, or you see spillage at the top or sides, a 34C likely fits better.
• If your 34C cups gap or wrinkle, especially at the top, a 34B may be the closer match.
• If the band on either feels right but the cup doesn’t, don’t change the band just move up or down a cup letter.

Quick way to check

Measure your bust at the fullest point and subtract your band size (34). A 2-inch difference points to a B cup; a 3-inch difference points to a C cup.

Not sure where you land? Try our Bra Size by Measurement Calculator for an instant answer, or use our Bra Size Comparison Tool to see the two sizes side by side.