Bra Size Calculator
Your bra size has two parts: the band, which comes from the measurement right under your bust, and the cup, which comes from the difference between your bust measurement and that band. Enter both measurements and the calculator gives your US and EU size, plus your sister sizes.
Your size
US: EU:
Sister sizes (same cup volume):
This calculator gives an estimate. Sizes vary between brands and do not replace a professional fitting.
How to measure yourself in 3 steps
- Stand up, wearing an unpadded bra or no bra, and wrap a flexible tape measure around your chest.
- Measure around the ribcage right under the bust, with the tape snug and level. That is your underbust.
- Measure around the fullest part of the bust without pulling the tape tight. That is your bust.
Which cup matches the difference
| Bust − band difference | Cup (US) |
|---|---|
| 1 inch (2.5 cm) | A |
| 2 inches (5 cm) | B |
| 3 inches (7.5 cm) | C |
| 4 inches (10 cm) | D |
| 5 inches (12.5 cm) | DD (E) |
| 6 inches (15 cm) | DDD (F) |
What sister sizes are
They are sizes with the same cup volume but a different band. If a band feels loose, try the smaller band with a larger cup; if it feels tight, the bigger band with a smaller cup. For example, 32C, 30D and 34B hold the same volume.
Frequently asked questions
How often should I re-measure?
Every six to twelve months, and always after a weight change, pregnancy, nursing or surgery. Bodies change more than you think.
Why does my size change between brands?
Each brand calculates cups and patterns its own way and fabrics stretch differently. Use this size as a starting point and always check the brand's size chart.
Should I measure with or without a bra?
The most reliable way is wearing an unpadded bra or none, standing with your arms relaxed.
How do I measure after a mastectomy?
A certified prosthetist or a specialty store can measure you and fit the prosthesis or pocketed bra. Your medical team tells you when it is safe to wear them. You can read the breast forms guide.
Does it work for choosing shapewear or an enhancer?
No: shapewear is sized by waist and hips and each brand has its own chart. This calculator is for bras only.