How to Find Your Bra Size
Measure your bust and band circumference, then use the calculator above. The difference between bust and band determines your cup size.
Measuring Tips
- Bust: Measure loosely around the fullest part of the chest while wearing a bra
- Band: Measure firmly (not tightly) directly under the breasts
- Stand straight with arms at your sides
- Keep the tape level all the way around
- Measure to the nearest 1/4 inch or 1/2 cm
Cup Size Chart (US)
- AA: Less than 1 inch difference
- A: 1 inch difference
- B: 2 inch difference
- C: 3 inch difference
- D: 4 inch difference
- DD/E: 5 inch difference
- DDD/F: 6 inch difference
Signs of a Poor Fit
- Band rides up in the back — band is too large, go down a size
- Straps dig in or fall off — band isn't supporting enough, try a smaller band
- Cups overflow or gape — wrong cup size or shape for your body
- Underwire sits on breast tissue — cup is too small or wrong style
Studies suggest 70-85% of women wear incorrectly fitted bras, most commonly a band too large and cup too small.
Understanding Sister Sizes
Sister sizes share the same cup volume but with different band sizes. If your exact size isn't available, sister sizes offer an alternative fit.
- Up one band, down one cup: 34C → 36B
- Down one band, up one cup: 34C → 32D
- Only move 1-2 sister sizes — beyond that, proportions change too much
Cup volume is relative to band size. A 32D and 36B hold the same volume, but the band length and wire width differ significantly.
International Size Conversion
- US/UK bands: Same numbering (32, 34, 36). Cup letters diverge above D (US DD = UK DD, US DDD = UK E)
- EU: Uses centimeters (US 32 = EU 70, US 34 = EU 75, US 36 = EU 80)
- France: EU band + 15 (US 34 = EU 75 = FR 90)
- Australia: Uses numbered back sizing (AU 10 = US 32, AU 12 = US 34)
Sizing varies between manufacturers even within the same country. Always try before buying when switching brands.
When to Get Remeasured
Measure every 6-12 months, or sooner after weight changes of 5+ lbs, pregnancy, breastfeeding, hormonal changes (menopause, starting/stopping birth control), or whenever your current bra feels uncomfortable.
Bra Types and When to Wear Them
- T-shirt bra: Molded cups with no visible seams. Best under fitted tops and lightweight fabrics
- Balconette: Wide-set straps with a horizontal neckline. Works with wide or square necklines
- Plunge: Deep V neckline between cups. Designed for low-cut tops and dresses
- Sports bra: Compression or encapsulation design for exercise. Should minimize bounce without restricting breathing
- Bralette: Unstructured, no underwire. Best for smaller cup sizes or loungewear
- Strapless: Relies entirely on band support. Band fit is critical — go down a band size for security
Band Lifespan and Care
Most bras last 6-12 months of regular wear before the elastic loses support. The band does 80% of the support work (not the straps), so a worn-out band means the entire bra is ineffective. To extend lifespan: hand wash or use a lingerie bag on the delicate cycle, air dry instead of machine drying, and rotate between at least 3 bras so each gets rest between wears. Hook on the loosest setting when new — as the band stretches over time, tighten to the middle and then innermost hooks.