Bra Size Calculator
Find your correct bra size by entering band and bust measurements in inches. Free online bra size calculator for US sizing with cup size determination and fit guidance.
About This Calculator
Finding the correct bra size is essential for comfort, support, and confidence. This bra size calculator helps you determine your US bra size by entering two simple measurements: your band (underbust) measurement and your bust measurement in inches. Whether you are shopping online, between sizes, or simply want to confirm your current fit, this tool provides an accurate starting point based on standard bra sizing formulas used across the lingerie industry.
The calculator rounds your band measurement to the nearest even number and computes the difference between your bust and band measurements to determine your cup size. Each inch of difference corresponds to one cup size increment, from AA (less than 1 inch) through A, B, C, D, DD, DDD, and beyond up to J cup. The final result displays your band size, bust size, cup size, and recommended full bra size.
Bra sizing is not an exact science — different brands use different sizing charts, and even the same brand may vary between styles. That is why we also explain sister sizes: bra sizes that have the same cup volume but different band lengths. For example, a 34C has the same cup volume as 32D and 36B. If a bra fits well in the cup but the band is too loose or tight, trying a sister size can help you find the perfect fit without changing cup volume.
Regional Notes
United States: US bra sizing follows inch-based measurements with cup sizes AA, A, B, C, D, DD (E), DDD (F), G, H, I, J. Band sizes range from 28 to 48 inches. Major retailers like Victoria's Secret, ThirdLove, and Aerie use this system.
United Kingdom: UK sizing shares the same inch-based band measurements but uses different cup letters beyond D: DD, E, F, FF, G, GG, H, HH, J. Brands like Marks & Spencer and Panache use the UK system.
India: Bra sizes in India typically follow UK sizing due to historical British influence, though international brands may use US or EU sizing. Most Indian lingerie stores carry sizes from 30 to 40 bands with cups A through DD.
For best results, measure yourself while braless or wearing a non-padded bra. Use a soft measuring tape and keep it level around your torso. The band measurement should be snug, while the bust measurement should be loose enough to breathe comfortably. If you are between sizes, always try the larger cup size first for a better fit.
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) directly under your bust, keeping the tape snug and level. Then measure the fullest part of your bust. Subtract your band measurement from your bust measurement to determine your cup size. Round your band measurement to the nearest even number.
What cup sizes does this calculator support?
This calculator supports US cup sizes from AA through J, covering the full range of standard sizing. The cup size is determined by the difference between your bust and band measurements in inches, with each inch representing one cup size increment.
How do I convert US bra sizes to UK or EU sizes?
US and UK band sizes are the same (inches), but cup letters differ. US DD equals UK DD, US DDD equals UK E, and US DDDD/G equals UK F. EU sizes use centimeters for the band and a different cup progression. Many online conversion charts can help you translate between sizing systems.
What are sister sizes in bras?
Sister sizes are bra sizes where the cup volume stays the same but the band length changes. For example, 34C, 32D, and 36B are sister sizes with identical cup volumes. If a bra fits well in the cup but the band is too tight or loose, trying a sister size can help you find the perfect fit.
Why is my calculated bra size different from my usual size?
Bra sizes can vary between brands, styles, and even different bras from the same manufacturer. Weight changes, hormonal fluctuations, and aging also affect breast size. The calculator provides a starting point based on your current measurements, but trying on bras is the most reliable way to find the best fit.
How tight should the band measurement be?
The band should be snug but not uncomfortable. You should be able to slide one finger comfortably underneath the band. The band provides most of the bra's support, so it should sit horizontally across your back without riding up. If the band rides up, try a smaller band size and larger cup size (sister size).
Can I use centimeters instead of inches?
Convert centimeters to inches by dividing by 2.54. Standard US bra sizing is based on inches, so accurate conversion is important. Many bra size calculators including this one work with inches. If you measure in centimeters, convert before entering your measurements.
What if my bust and band measurements give the same number?
If your bust and band measurements are equal (difference of less than 1 inch), your cup size is AA. This is common for smaller bust sizes. The calculator handles this correctly and will show AA as your cup size. Focus on finding bras with a comfortable band fit and consider trying padded or push-up styles for shape.