Bra Size Calculator
This free bra size calculator helps you estimate your US band and cup size using two measurements: underbust and overbust. Use it as a fast starting point before trying brand-specific fits.
How to Measure Bra Size at Home
- Measure your underbust: Wrap a soft tape snugly around your ribcage, directly under your bust.
- Measure your overbust: Measure around the fullest part of your bust while standing naturally.
- Choose inches or centimeters: Enter values in your preferred unit. The calculator supports both in and cm.
- Get your estimated bra size: Review your suggested band, cup, and sister sizes, then compare with brand fit notes.
Cup Size Difference Reference
Cup size is typically estimated from the difference between overbust and underbust measurements.
| Difference | Estimated Cup |
|---|---|
| 1 in | A |
| 2 in | B |
| 3 in | C |
| 4 in | D |
| 5 in | DD |
| 6 in | DDD/F |
| 7 in | G |
| 8 in | H |
Frequently Asked Questions
How accurate is this bra size calculator?
It gives a reliable starting size based on your two measurements. Final fit can vary by brand, bra style, and fabric stretch, so it is best to confirm with a fitting.
What if my overbust is not larger than underbust?
Double-check your tape position and keep it level around your body. The overbust value should usually be larger than underbust for a valid cup-size estimate.
Can I use centimeters instead of inches?
Yes. Select centimeters in the unit option and the calculator converts values automatically before estimating band and cup size.
What are sister sizes in bras?
Sister sizes are alternate bra sizes with a similar cup volume. For example, going down one band size and up one cup size can provide a similar cup fit with a tighter band.