What Is a Bra Size Calculator?
This calculator estimates a US bra size from two simple measurements: your band size (under the bust) and bust size (at the fullest point) — a common starting point for finding a well-fitting bra, though in-person fitting is often more accurate due to variation between brands and styles.
How to Use the Bra Size Calculator
- Measure your band snugly around your ribcage, just under your bust.
- Measure around the fullest part of your bust.
- View your estimated size.
Bra Size Formula
Worked Example
Band size: 32
Difference: 36 − 32 = 4 inches → roughly a D cup (each inch ≈ one cup letter: A=1, B=2, C=3, D=4)
Estimated size: 32D
Understanding Your Results
This provides a general starting estimate. Bra sizing varies noticeably between brands and styles, and many people find their true best fit through trying on multiple sizes or a professional fitting, since posture, band stretch, and individual body shape all affect actual fit.
Common Mistakes to Avoid
- Measuring the band too loosely — it should be snug but not tight.
- Assuming size is identical across all brands — cup and band sizing conventions vary.
Frequently Asked Questions
Measure your band snugly around your ribcage directly under your bust, and separately measure around the fullest part of your bust — both while wearing a well-fitting, non-padded bra for best accuracy.
Cup size is generally based on the difference between bust and band measurements — each inch of difference typically corresponds to one cup letter (1 inch ≈ A, 2 inches ≈ B, and so on), though exact conventions vary by brand.
There's no single universal sizing standard, so cut, construction, and sizing conventions differ meaningfully between manufacturers — the same labeled size can fit differently across brands.
A professional fitting can account for factors a simple calculator can't, like cup shape and individual proportions, and is often recommended for the most accurate results.
Body changes over time (weight changes, pregnancy, aging) can affect size, so re-measuring periodically or when a bra no longer fits comfortably is a reasonable practice.