Studies show that 70–80% of women wear the wrong bra size — leading to discomfort, poor posture, and inadequate support. Our free Bra Size Calculator helps you find your correct size in US, UK, and EU sizing using just two measurements. No guessing, no brand inconsistency — just accurate results.
Bra Size Calculator
Bra Size Calculator
Measure in inches while wearing a non-padded bra or no bra. Keep tape snug but not tight.
How to Measure for a Bra – Step by Step
- Band measurement (underbust): Wrap the tape measure snugly around your ribcage, directly under your bust. Keep it horizontal and parallel to the floor. Round to the nearest half inch.
- Bust measurement: Lean forward at 90° and wrap the tape loosely around the fullest part of your bust. This leaning method gives the most accurate cup measurement.
- Enter both measurements above and hit Calculate.
Bra Size Chart – US Cup Sizes
| Bust − Band Difference | US Cup Size | UK Cup Size |
|---|---|---|
| 0–1 inch | AA | AA |
| 1 inch | A | A |
| 2 inches | B | B |
| 3 inches | C | C |
| 4 inches | D | D |
| 5 inches | DD | DD |
| 6 inches | DDD/F | E |
| 7 inches | G | F |
What Are Sister Sizes?
Sister sizes are bra sizes with the same cup volume but different band sizes. If a 34C fits in the band but the cup is too small, try a 36B (larger band, smaller cup letter — same actual cup volume). This is useful when your size is hard to find in stores.
- 34C sisters: 32D (smaller band) and 36B (larger band)
- 36D sisters: 34DD and 38C
- 38DDD sisters: 36G and 40DD
Signs Your Bra Doesn’t Fit Correctly
- Band rides up in back: Band is too large — go down a band size, up a cup size
- Straps dig in or fall off: You’re relying on straps instead of band support
- Cup spillage or side boob: Cup is too small — go up a cup size
- Gaping cups: Cup is too large or wrong shape for your breast type
- Underwire pokes: Cup too small or wrong style for your breast width
Frequently Asked Questions
Do bra sizes vary by brand?
Yes, significantly. Victoria’s Secret, for example, tends to measure differently than UK brands like Bravissimo. Always try on before buying or check the brand’s specific size chart. Your calculator size is a starting point — expect to try one size up or down.
Does bra size change with weight?
Yes. Breast tissue changes with weight fluctuation, pregnancy, breastfeeding, and hormonal changes. Remeasure every 12–18 months or after any significant body change.
What is the most common bra size?
In the US, the most commonly purchased bra size is 34B — but fitting experts argue the most common correct size is closer to 34DD based on proper measurement methods.