34A Bra Size: What It Means and How It Should Fit

A 34A bra has a 34-inch band and an A cup, which means your bust measures about 1 inch more than your band, roughly 35 inches. Your underbust is just over 32 up to 34 inches.

What does 34A mean?

34 is the band size, measured snugly around your ribcage. A is the first full cup step, a 1-inch difference between bust and band. B is 2 inches, C is 3, and so on.

A 34A cup holds roughly the same volume as a 32B or a 30C. Those are its sister sizes. So “A cup” on a 34 band isn’t the smallest cup a person can wear; it’s a modest cup on a mid-range band. The bra size chart shows every step.

What measurements give you a 34A?

1. Measure snugly around your ribcage under the bust. Round up to the next even number. Just over 32 up to 34 inches gives a 34 band.
2. Measure around the fullest part of your bust without squashing. Round to the nearest inch.
3. Subtract: 35 − 34 = 1 inch, an A cup.

If your bust and underbust are almost the same, our calculator will tell you the result falls below an A cup. Our guide to measuring your bra size explains how to measure accurately.

Were you sized with “plus four”?

Many people wear 34A because a store added 4 or 5 inches to their underbust. Someone with a 30-inch underbust and a 35-inch bust gets 34A that way, but 30DD (5 inches) under our method. The 34A band is 4 inches looser, and its cups are two sizes smaller than the 30DD’s (the same cup volume on a 34 band would be 34C). If your 34A band floats up your back, measure again.

What are the sister sizes of 34A?

The sister sizes of 34A are 32B and 36AA.

• 32B: same cups, tighter band. A good first step if the band feels loose.
• 36AA: same cups, looser band. Fewer brands make AA cups, so check the size range first.

The sister size calculator lists the full diagonal.

How to stop 34A cups from gaping

Gaping is the number one 34A fit issue. Before dropping a cup size, try these in order:

1. Tighten the band. A loose band lets the cups tip forward. Try the tightest hook or 32B.
2. Change the cup shape. Plunge and demi bras have less fabric at the top, so there’s less to gape. Full-coverage molded cups gape most.
3. Try light lining. Thin foam keeps its shape and doesn’t wrinkle like unlined fabric.
4. Lean forward to put it on. Scooping tissue into the cup fills it properly. Our guide on how to put on a bra shows the method.

Which bra styles suit a 34A?

• Push-up bras add lift and fullness with angled padding. Read what a push-up bra does.
• Plunge and demi bras for lower necklines with less top coverage.
• Bralettes give soft, comfortable support most A cups find plenty.
• Lightly lined T-shirt bras for a smooth look under knits.

Signs 34A isn’t your size