Bra Size Calculator

Calculate bra size from band and bust measurements. See sister sizes for alternative fit.
in
in

Your Size

34C

Band

34

Cup

C

Size Details

Band Size34
Cup SizeC
Full Size34C
Bust − Band Difference3.0 inches

Sister Sizes

Sister sizes have the same cup volume but different band lengths. Try these if your size is unavailable.

Band Down, Cup Up

32D

Your Size

34C

Band Up, Cup Down

36B

Use the Bra Size Calculator above to calculate your results. Enter your values and see instant results — all calculations run in your browser.

Disclaimer: This calculator is for informational purposes only and does not constitute tax, financial, or legal advice. Results are estimates based on the information you provide and current rates. Always consult a qualified tax professional or financial advisor for advice specific to your situation.

How It Works

Our 2026 Bra Size Calculator helps you find your ideal bra size based on your unique band and bust measurements. This is crucial as a properly fitting bra provides better support, comfort, and can even improve posture, preventing common issues like back pain that affect over 60% of women in ill-fitting bras. Get ready to experience the difference a well-fitted bra makes in your daily life.

To calculate your bra size, we use a two-step methodology. First, your underbust measurement (band size) is rounded to the nearest even number for band sizes 30 and up, or specific odd numbers for smaller bands based on industry standards. Second, your bust measurement is subtracted from your band measurement to determine your cup size, with each inch difference corresponding to a letter increment (e.g., 1 inch = A, 2 inches = B).

Remember that bra sizes can vary slightly between brands, so always try on bras if possible. Avoid common mistakes like measuring over clothing or pulling the tape measure too tightly or loosely. This calculator provides a great starting point, but your comfort is the ultimate guide to the perfect fit.

Example: Finding Your Perfect Fit

  1. 1 Measure your underbust tightly: 31 inches. Measure your bust at its fullest point: 37 inches.
  2. 2 Band Size Calculation: 31 inches rounds up to a 32 band. Cup Size Calculation: 37 inches (bust) - 32 inches (band) = 5 inches difference.
  3. 3 This results in a calculated bra size of 32DD.
  4. 4 Sister Sizes: If a 32DD isn't comfortable or available, consider trying sister sizes like 34D (one band size up, one cup size down) or 30E (one band size down, one cup size up) for an alternative fit. These sizes offer a similar cup volume with different band tensions.

Source: BLS · Last updated: April 2026

Frequently Asked Questions

How do I measure my bra size at home?
Measure your underbust snugly for the band size (round to nearest even number) and your bust at the fullest point. The difference in inches determines the cup: 1 inch = A, 2 inches = B, 3 inches = C, 4 inches = D.
What is a sister size in bras?
Sister sizes have the same cup volume with a different band. Going up a band size means going down a cup letter, and vice versa. For example, 34C, 32D, and 36B are all sister sizes with the same cup volume.
Why does my bra size vary between brands?
There is no universal bra sizing standard, so a 34C in one brand may fit like a 32D in another. European brands use centimeters while US brands use inches, adding further variation.

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