Finding the right bra size can feel confusing, but once you understand how the sizing system works, it becomes much easier. Bra sizes are a combination of numbers and letters, and together, they tell you two things: the size of your band (the part that goes around your chest) and the size of your cup (which holds the breast tissue).

1. The Basics of Bra Sizing

A bra size usually looks like this: 34B, 36C, 32D, etc.

• The number (e.g., 32, 34, 36, 38) refers to the band size.

• The letter (A, B, C, D, etc.) refers to the cup size.

For example, if you wear a 34C:

• “34” = band size

• “C” = cup size

2. How to Measure Bra Size at Home

Step 1: Measure the Band Size

• Take a measuring tape and wrap it snugly around your ribcage, just under your breasts.

• Round the measurement to the nearest whole number.

• If it’s 34 inches, your band size is 34.

Step 2: Measure the Bust Size

• Measure around the fullest part of your bust, keeping the tape level.

• Let’s say this comes to 37 inches.

Step 3: Calculate the Cup Size

• Subtract the band size from the bust size.

• Example: 37 (bust) – 34 (band) = 3 inches difference.

• Each inch difference corresponds to a cup size:

  • 1 inch = A cup

  • 2 inches = B cup

  • 3 inches = C cup

  • 4 inches = D cup

  • 5 inches = DD/E cup, and so on.

So in this case, 3 inches = C cup. Final size = 34C.

3. Understanding Band Sizes

The band provides most of the support, not the straps.

• Smaller band = tighter fit.

• Larger band = looser fit.

If your bra rides up at the back, your band might be too big. If it digs in uncomfortably, it may be too small.

4. Understanding Cup Sizes

Cup sizes are relative to the band size.

• A 34C and a 36C don’t hold the same breast volume.

• As the band size increases, the cup volume also increases.

• This is why a 34D is smaller than a 38D.

5. Sister Sizes (Alternative Fits)

Sometimes your size might feel tight or loose depending on the brand. That’s where sister sizes help.

• Sister sizes are bras with the same cup volume but different band sizes.

Example:

• If you wear a 34C, your sister sizes are 32D (tighter band, bigger cup) and 36B (looser band, smaller cup).

6. Signs You’re Wearing the Wrong Size

• Straps keep slipping off → Cup too big or straps too loose.

• Bra band rides up → Band too big.

• Breasts spill out of the cup → Cup too small.

• Gaps in the cup → Cup too big.

• Painful underwire → Wrong cup or band size.

7. Why Bra Sizes Differ Across Brands

Different brands use slightly different sizing charts. Just like clothing, a 34C in one brand might feel like a 36B in another. Always try on bras before buying or check each brand’s size guide.

8. Special Notes on Bra Sizing

• Sports bras often use S/M/L sizes instead of band and cup.

• European and UK sizing differ slightly from US sizing (for example, after D cup, UK sizes go D, DD, E, F, etc.).

• Pregnancy and weight changes can affect your bra size.