Bra Size Calculator – Find Your Estimated Bra Size
Estimate bra band and cup size from bust and underbust measurements.
About the Bra Size Calculator
What is the Bra Size Calculator?
A bra size calculator estimates your band and cup size from two measurements: the underbust and the fullest part of the bust.
Why use this calculator?
Getting the band right does most of the work in a well-fitting bra, and the difference between bust and underbust sets the cup.
How to use it
- Measure snugly around your ribcage under the bust for the underbust.
- Measure around the fullest part of your bust for the bust.
- Read the estimated band and cup.
Formula
Band is the underbust rounded to the nearest even number; cup comes from bust − underbust.
Sizing varies between brands and countries, so use this as a starting point and try sizes around it.
Frequently Asked Questions
How tight should the underbust measurement be?
Snug but not tight, with the tape level around your ribcage. If in doubt, measure both snug and loose.
Why does my size differ between brands?
Bra sizing is not perfectly standardized, so band and cup labelling varies. Always use the size as a starting point and adjust.
Is this a medical diagnosis?
No. This tool provides general wellness information only. It is not a substitute for evaluation by a qualified healthcare professional.
Why do results differ from my doctor's measurements?
Clinical measurements use calibrated equipment and professional technique. Home estimates rely on formulas and self-reported values, so small differences are normal.
How often should I recalculate?
Recheck after meaningful changes such as weight gain or loss, a new workout routine, or every few months to track trends over time.
Do these formulas apply to everyone?
Most population formulas are less accurate for athletes, pregnant people, very young children and the elderly. Use them as a general guide.
Is this calculator free to use?
Yes. Every calculator on this site is completely free, with no hidden fees, no subscriptions and no limits on how many times you can use it.
How accurate are the results?
We use standard, widely accepted formulas and calculate in your browser using double-precision arithmetic. Results are rounded for readability, so treat them as reliable estimates rather than a guarantee. Real-world factors can vary the true figure.
Can I add this calculator to my own website?
Yes. Open this calculator page and use the "Add to your website" box in the sidebar to copy a ready-made iframe snippet, then paste it into any HTML page.
Does it work on a phone or tablet?
Yes. The layout is fully responsive, so it works on desktops, laptops, tablets and mobile phones, and every input adapts to touch screens.