Bra Size Calculator
Free bra size calculator. Measure your band and bust to find your perfect bra size in US, UK, EU, and international sizing. Get sister size recommendations.
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How to Measure
Band Measurement (Under Bust): Measure snugly around your ribcage, directly under your bust. Keep the tape parallel to the ground.
Bust Measurement (Fullest Point): Measure around the fullest part of your bust, keeping the tape parallel to the ground. Don't pull too tight.
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Last updated: January 2026
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Frequently Asked Questions
How do I accurately measure myself for a bra?
Use a soft measuring tape and wear an unpadded bra or no bra. For band size, measure snugly around your ribcage directly under your bust, keeping the tape parallel to the floor. Round to the nearest whole number. For bust measurement, measure around the fullest part of your bust without pulling tight. The difference between these measurements determines your cup size: 1 inch = A cup, 2 inches = B cup, 3 inches = C cup, 4 inches = D cup, and so on.
What are sister sizes and when should I use them?
Sister sizes are bra sizes with the same cup volume but different band/cup combinations. For example, 34C, 32D, and 36B are sister sizes—they all have the same cup volume. If your band feels too tight, try going up a band size and down a cup size (34C → 36B). If the band feels too loose, go down a band size and up a cup size (34C → 32D). Sister sizes are helpful when your usual size isn't available or fits differently between brands.
How do US, UK, and EU bra sizes differ?
The main differences are in cup letter progression and band measurements. US and UK sizes use similar band numbers but diverge after D cup—US goes D, DD, DDD/F, G while UK goes D, DD, E, F, FF, G. EU sizes use centimeters for bands (32=70, 34=75, 36=80) and different cup letters. A US 34D equals UK 34D but EU 75D. Always check the brand's origin to use the correct sizing system, as wearing the wrong regional size can be off by 1-2 cup sizes.
How should a properly fitting bra feel?
A well-fitting bra has several key indicators: The band should be snug and level around your body (not riding up in back), staying put on the loosest hook when new. The center gore (front piece between cups) should lie flat against your sternum. Cups should fully contain breast tissue without spillage, gaping, or wrinkling. Straps should stay in place without digging in—they provide only 10% of support while the band provides 90%. You should be able to fit two fingers under the band comfortably.
How often should I get remeasured for a bra?
Bra size can change frequently, so remeasuring every 6-12 months is recommended. Common factors that affect size include weight changes of 10+ pounds, pregnancy and breastfeeding, hormonal changes during menstrual cycles, starting or stopping birth control, menopause, and changes in exercise routines. Additionally, bras stretch over time—a bra that fit on the loosest hook when new should eventually be worn on tighter hooks. When the tightest hook no longer provides support, it's time for a new bra.