Bra Size Calculator (cm)
Enter your measurements in centimeters to get an estimated EU and UK/US bra size.
Tip: Measure without a padded bra, keep tape level, and breathe normally.
How this bra size calculator in centimeters works
This calculator uses two body measurements: your underbust (ribcage) and your full bust. It estimates your band size and cup size, then displays a suggested size in both EU and UK/US formats. Because sizing varies by brand, this result is a strong starting point rather than an absolute final answer.
How to measure correctly (cm)
1) Underbust measurement
Wrap a soft tape measure around your ribcage directly under your bust. Keep the tape parallel to the floor and snug (not painful). Record this in centimeters.
2) Full bust measurement
Measure around the fullest part of your bust, keeping the tape level and comfortably loose. Stand naturally and do not hold your breath while measuring.
3) Calculate the difference
Subtract underbust from full bust. This difference helps determine cup size. In this calculator, cup progression is based on centimeter intervals commonly used in fitting charts.
Quick cup guide by difference (cm)
| Bust - Underbust Difference | Estimated Cup (EU) | Approx UK Cup |
|---|---|---|
| Less than 10 cm | AA | AA |
| 10 to < 12 cm | A | A |
| 12 to < 14 cm | B | B |
| 14 to < 16 cm | C | C |
| 16 to < 18 cm | D | D |
| 18 to < 20 cm | E | DD |
| 20 to < 22 cm | F | E |
| 22 to < 24 cm | G | F |
| 24 to < 26 cm | H | FF |
| 26 to < 28 cm | I | G |
Common fitting mistakes
- Measuring over thick clothing.
- Keeping tape too loose under the bust.
- Using only cup letter without band (for example, “D cup” alone).
- Ignoring brand differences and bra style differences.
- Not re-measuring after body changes, training, or hormonal changes.
Understanding sister sizes
Sister sizes are nearby sizes with similar cup volume. If the band feels too tight, go up one band size and down one cup. If the band feels too loose, go down one band size and up one cup. Example: if 75C feels tight in the band, try 80B. If it feels loose, try 70D.
When to adjust the calculator result
Go up in cup if:
- Breast tissue spills over the top or sides.
- Center gore does not sit flat against your chest.
Go down in cup if:
- Cup fabric wrinkles or gaps significantly.
- The cup feels empty near the apex.
Adjust band if:
- Band rides up your back (too loose).
- You cannot comfortably fit two fingers under the band (possibly too tight).
Final note
The best bra size is the one that supports you comfortably for your body and your use case (daily wear, sports, nursing, or special occasion). Use this centimeter calculator as your baseline, then fine-tune with real try-ons.