Bra Size Calculator
Find your perfect bra size instantly. Enter band and bust measurements for US standard bra sizing. Free online bra size calculator with cup size chart and fitting tips.
About This Calculator
Finding the right bra size is essential for comfort, support, and confidence. Our free Bra Size Calculator helps you determine your correct bra size at home using just two simple measurements — your band (underbust) and bust measurements. Whether you are shopping for new lingerie, checking your current fit, or simply curious about your size, this tool provides instant results based on standard US bra sizing conventions.
The calculator works by taking your band measurement (the snug circumference around your ribcage directly under your bust) and your bust measurement (the looser circumference around the fullest part of your bust). It then calculates your band size by rounding to the nearest even number and determines your cup size by finding the difference between your bust and band measurements. Each inch of difference corresponds to a cup size — 1 inch is an A cup, 2 inches is a B cup, 3 inches is a C cup, and so on.
Regional Notes
United States: US bra sizing uses inches for band measurements and standard cup letters (AA, A, B, C, D, DD, DDD, F, G, H, I, J). This calculator defaults to US sizing conventions, which are the most common standard used in American lingerie brands.
United Kingdom: UK bra sizing also uses inches but follows a different cup progression. For example, a US DDD cup is equivalent to a UK E cup, and US DDDD/G equals UK F. When shopping British brands, you may need to convert your US size.
India and EU: European and Indian brands commonly use EU sizing with centimeter measurements. Band sizes are measured in cm with 5 cm increments (70, 75, 80, 85, etc.). A US 34 band roughly corresponds to EU 75. Cup conversions also differ between systems.
Remember that bra sizes can vary between manufacturers and even between different styles from the same brand. Use this calculator as a starting point, and always try on bras whenever possible to ensure the best fit. Factors such as breast shape, band elasticity, and cup design all affect how a bra fits your unique body.
Frequently Asked Questions
How do I measure my bra size at home?
To measure your bra size at home, use a soft measuring tape. First measure your underbust (band) snugly around your ribcage. Then measure your bust at the fullest point. Enter both measurements into this calculator to get your size instantly.
What is the difference between US, UK, and EU bra sizes?
US, UK, and EU bra sizes differ in band measurement units (inches vs cm) and cup labeling. US sizes use inches for band and letters A-DD-DDD for cups. UK sizes also use inches but use A-DD-E-F-FF for cups. EU sizes use centimeters for band with 5 cm increments and a different cup progression. This calculator uses US standard sizing.
What are sister sizes in bras?
Sister sizes are bra sizes that have the same cup volume but different band lengths. For example, 34C, 32D, and 36B are sister sizes with identical cup volume. If a bra band feels too tight or too loose, trying a sister size can help you find a better fit.
How accurate is this bra size calculator?
This calculator provides an accurate estimate based on standard US bra sizing formulas. However, fit may vary across brands, styles, and individual body shapes. Professional fitting is recommended for the best results.
Should I measure wearing a bra or without?
For the most accurate measurements, measure while braless or wearing a non-padded, non-push-up bra. This ensures the tape sits against your natural shape and gives the most reliable band and bust measurements.
How tight should the measuring tape be for band measurement?
The tape should be snug but not tight — you should be able to slide one finger underneath. The band provides most of the bra's support, so an accurate underbust measurement is crucial for finding the right band size.
What if my bust measurement is in between cup sizes?
If your bust measurement falls between two cup sizes, round up to the nearest whole number. It is generally better to try the larger cup size first, as a slightly larger cup is more comfortable than one that is too small.