Find Your Estimated Bra Size
Enter your measurements to get a starting-point bra size. For best results, measure while braless or in a thin, unpadded bra.
Note: This calculator gives an estimate. Brand sizing, breast shape, and style (balconette, plunge, sports, etc.) can all affect fit.
How to Measure for Bra Size at Home
A bra size has two main parts: band size and cup size. The band is the number (like 32, 34, 36), and the cup is the letter (like B, C, D). The calculator above uses your underbust and full bust measurements to estimate both.
To measure accurately, use a soft tape measure and keep it level all the way around your body. Stand naturally, breathe normally, and avoid pulling the tape too tight.
Step-by-Step Measuring Guide
- 1) Underbust: Wrap the tape snugly around your ribcage, directly under your bust.
- 2) Full bust: Measure around the fullest part of your bust with the tape parallel to the floor.
- 3) Enter values: Input both numbers in inches or centimeters.
- 4) Calculate: The tool will estimate your bra size and suggest sister sizes.
How This Bra Size Calculator Works
The calculator estimates your size in a few simple steps:
- Converts measurements to inches (if needed).
- Calculates a band size by rounding to the nearest even number.
- Finds cup size from the difference between bust and underbust (or bust and band in traditional mode).
- Displays an estimated US/UK size plus a rough EU band equivalent.
If your result feels slightly off, that is normal. Bra sizing is not perfectly standardized across manufacturers.
Cup Difference Quick Reference (Approximate)
- ~1 inch difference: A cup
- ~2 inches: B cup
- ~3 inches: C cup
- ~4 inches: D cup
- ~5 inches: DD/E cup
- ~6 inches: DDD/F cup
What Are Sister Sizes?
Sister sizes have similar cup volume but different band tightness. For example, if 34D feels too tight in the band, you might try 36C. If it feels too loose, you could test 32DD.
This is useful when:
- A brand runs tight or loose in the band.
- You are between sizes.
- You prefer a firmer or softer fit depending on bra style.
Signs Your Bra Fits Well
Band Fit
- The band sits level and does not ride up in back.
- You can fit about two fingers under the band comfortably.
- Most support should come from the band, not the straps.
Cup Fit
- No gaping at the top of the cup.
- No spilling over the top or sides.
- Underwire (if present) lies around the breast tissue, not on it.
Straps and Center Gore
- Straps should not dig in or slip constantly.
- The center gore should lie flat against the sternum (for wired bras).
Common Bra Sizing Mistakes
- Only buying one size forever: Body measurements can change over time.
- Ignoring band wear: Bands stretch out; replace bras when support declines.
- Choosing cup by letter alone: A “D cup” is not the same volume on every band.
- Over-tightening straps: This can cause shoulder strain and poor support distribution.
FAQ
Is this calculator accurate?
It is a strong starting point for most people. Final fit depends on shape, tissue distribution, brand differences, and bra construction.
Should I use modern or traditional sizing?
Modern sizing is usually preferred today. Traditional (+4) can still be useful with some brands or personal fit preferences.
Can I use this for sports bras?
Yes, as a baseline. Sports bras may fit tighter in the band and vary by impact level (low, medium, high support).
What if I am between sizes?
Try your calculated size first, then test sister sizes for comfort and support.
Final Thoughts
A good bra size can improve comfort, posture, and confidence. Use the calculator to narrow your options quickly, then do a real-world fit check in the style you wear most often. If possible, compare two nearby sizes side-by-side and keep the one that feels secure, smooth, and comfortable for several hours.