Bra Size Calculator
Find your perfect fit instantly. Use our calculator to determine your accurate band and cup size based on professional fitting standards.
Based on your measurements, we suggest:
Sister Size (Up)
--Larger band, smaller cup
Sister Size (Down)
--Smaller band, larger cup
International Conversions
How to Use the Bra Size Calculator
A bra size calculator determines bra size by measuring band and bust circumference. Calculate band size by rounding the underbust measurement to the nearest even number. Calculate cup size by subtracting band from bust; each 1-inch difference equals one cup size (A=1 inch, B=2 inches, C=3 inches).
Finding the right bra size depends on accurate measurement of your bust and underbust. A precise fitting ensures comfort, support, and a better silhouette. Follow these steps to estimate your correct cup and band volume.
Measure Your Underbust
Wrap a soft measuring tape snugly around your ribcage, directly under your breasts. Keep the tape level and pull it as tight as you'd like your bra band to feel. Enter this value as your underbust.
Measure Your Full Bust
Measure around the fullest part of your bust (usually across the nipples). Hold the tape loosely so it doesn't compress your breast tissue. This measurement determines your cup size when compared to the band.
Get Your Results
Click the button to see your primary size. We also provide "Sister Sizes"—alternative combinations that have the same cup volume but different band lengths.
Cup Size Chart (Inches)
Cup size is determined by the difference between your bust and band measurement:
| Difference (In) | US/UK Cup | EU/Intl Cup |
|---|---|---|
| 0 - 1 | A | A |
| 1 - 2 | B | B |
| 2 - 3 | C | C |
| 3 - 4 | D | D |
| 4 - 5 | DD / E | E |
| 5 - 6 | DDD / F | F |
Real Example Use Cases
Buying Online
If you're shopping for a premium lingerie brand but aren't sure of your current measurements, use the calculator to avoid the hassle of returns. Knowing your width and bust volume helps you pick the right material stretch for your frame.
Post-Pregnancy Fitting
Body shapes change significantly after major life events. A quick measurement of your underbust and bust can estimate a new band and cup combination that offers the support you need during recovery.
International Travel Shopping
Different regions use varying size labels. Use our calculator to convert your standard size into European (EU), French (FR), or Japanese (JP) metrics before you head into a boutique abroad.
Bra Fitting Statistics
80%
Of women are wearing the wrong bra size according to industry fitting studies.
70%
Of fitters find that women wear a band that is too large and cups that are too small.
6-12 Mos
The average lifespan of a high-quality bra before the band lose elasticity.
1 in 3
Women experience breast pain often caused by improper support and poor fit.
Frequently asked questions (FAQ)
How often should I recalculate my bra size?
You should use a bra size calculator to check your sizing every six months. Factors like weight change, hormonal shifts, and even certain types of exercise can alter your bust and underbust measurement, requiring a new bra fitting estimate to maintain optimal comfort.
What are "sister sizes" in the context of this calculator?
Sister sizes are groups of size labels that share the same cup volume. For example, a 34C has the same volume as a 36B. If a band feels too tight but the cup fits perfectly, you might go up in band size and down in cup letter according to our guide to maintain the same fit.
How do I know if the band size is correct?
The band provides most of the support in lingerie. It should be level around your body and firm enough that you can only fit two fingers underneath it. If the measurement of your underbust was accurate, the band size should sit comfortably without riding up or sacrificing comfort.
Why does my cup size change between different brands?
Standardization varies between lingerie manufacturers and the material used in the bra. While the calculator gives a mathematical estimate, different styles might require an intentional conversion or a different cup size depth to achieve a proper bra fitting.
What should I do if my measurements fall between two sizes?
If your underbust measurement falls between two even numbers, it is best to try both band size options. Because lingerie material elasticity varies, you might prefer a tighter fitting for support or a looser one for daily comfort. If your bust volume is between cup letters, choosing the larger sizing usually prevents overflow.
How does body shape affect the results of a bra size calculator?
A calculator provides a mathematical estimate based on circumference, but it cannot account for individual body shape. Your unique bust volume distribution—whether fuller at the bottom or the top—might require a different cup size depth than the numerical sizing suggests in our guide.
Can significant weight changes affect my band and cup measurements?
Yes. Weight fluctuations directly impact your underbust and bust measurement. A change of even 5 to 10 pounds can alter your band size. Since cup size is relative to the band, you should update your fitting estimate frequently to ensure your bra continues to provide adequate support and sizing accuracy.
Does this calculator apply to specialized bras like sports or maternity styles?
This tool provides a standard sizing base, but specialized bras often have different requirements. Sports lingerie uses tighter material for high support, and maternity styles account for fluctuating bust volume. Use the calculator as a guide, but always refer to specialized brand charts for a better fit.