Bra Size Calculator
Bra Size Calculator
Enter your underbust and bust measurements to get an estimated starting bra size, sister sizes, and size conversions. You can use inches or centimeters.
Your Estimated Bra Size
Your Sister Sizes
Sister sizes have different band numbers but a similar cup volume. They can be useful when the band or cup of your starting size does not feel right.
International Bra Size Conversion
Bra labels can use different sizing systems. Use this table as a convenient starting reference when shopping internationally.
| Size System | Estimated Size |
|---|---|
| US | — |
| UK | — |
| EU | — |
| Australia | — |
International conversions are approximate because brands can use different grading and labeling conventions. Always check the individual brand’s size chart.
How to Measure Your Bra Size at Home
1. Measure Your Underbust
Stand naturally and wrap a soft measuring tape around your ribcage, directly underneath your bust. Keep the tape level all the way around your body and snug without pulling it uncomfortably tight.
2. Measure Your Bust
Place the tape around the fullest part of your bust. Keep it level and comfortably snug rather than compressing your breast tissue.
3. Enter Both Measurements
Enter the numbers above using the same measurement unit. The calculator uses the relationship between your ribcage and bust measurements to estimate a starting band and cup size.
4. Check the Actual Fit
Your calculated size is only a starting point. Different brands and bra styles can fit differently, so use the manufacturer’s size chart whenever possible.
How Should a Bra Fit?
Band
The band should feel secure and sit level around your body without riding up or causing painful pressure.
Cups
Your breasts should sit comfortably inside the cups without obvious spilling or large areas of empty space.
Straps
Straps should stay comfortably on your shoulders without digging in. They should not have to provide all the support.
Center Gore
On many underwire styles, the center section should sit comfortably against the breastbone rather than digging into breast tissue.
What to Do If Your Bra Does Not Fit
| Problem | Possible Starting Adjustment |
|---|---|
| Band rides up | Try a smaller band with the corresponding sister cup. |
| Band feels very tight | Try a larger band and the corresponding sister cup. |
| Cups overflow | Try a larger cup while keeping the band the same. |
| Cups gape | Try a smaller cup or a different cup shape. |
| Straps constantly slip | Adjust the straps and check the band and bra style. |
| Underwire digs in | Try a different size or cup shape with a better wire width. |
What Is a Bra Size?
A bra size normally combines a band measurement with a cup letter. The band refers to the measurement around your torso underneath the bust, while the cup indicates the relative difference between the bust measurement and the band measurement.
This is why the cup letter cannot be considered by itself. A C cup on one band size does not necessarily have the same cup volume as a C cup on another band size.
How Does This Bra Size Calculator Work?
The calculator uses two measurements: your underbust and the fullest part of your bust. It then estimates a band size and cup size using a traditional sizing approach.
Because manufacturers use different patterns, materials and sizing conventions, the result should be treated as a useful starting point rather than a promise that every bra in that size will fit identically. Professional fitting guides also emphasize checking the actual band, cups, straps and underwire after trying a bra on. :contentReference[oaicite:1]{index=1}
Why Is Measuring Your Underbust Important?
The band provides much of the support in a properly fitted bra. Your underbust measurement gives you an important starting point for selecting the band.
Keep the tape level around your torso and snug rather than painfully tight. A consistent measurement makes the calculator more useful when you compare different brands and styles. :contentReference[oaicite:2]{index=2}
Why Does My Bra Size Change Between Brands?
Bra sizing is not perfectly standardized across every manufacturer. Different brands can use different cup shapes, wire widths, fabrics, grading methods and sizing charts.
That means your calculated size should be used as a starting point. When buying a new style, compare your measurements with that brand’s own chart and pay attention to how the finished bra actually fits.
What Are Sister Sizes?
Sister sizes are sizes with different band numbers but related cup volume. They can be helpful when the cup seems right but the band does not feel comfortable.
For example, moving to a smaller band generally requires moving to a larger cup letter to maintain a similar cup volume. Moving to a larger band works in the opposite direction. The exact result can still vary with the design and manufacturer. :contentReference[oaicite:3]{index=3}
Should You Measure With or Without a Bra?
For a home measurement, many fitting guides recommend using a soft tape and either going braless or wearing a non-padded bra so thick padding does not alter the measurement. Keep your posture natural and breathe normally. :contentReference[oaicite:4]{index=4}
Why Does My Calculated Size Feel Wrong?
A measurement-based result cannot account for every factor that affects fit. Breast shape, tissue distribution, cup construction, underwire shape, padding and fabric can all influence comfort.
If the calculated size does not look or feel right, try the nearby sister size and consider a different bra style. A good fit should be evaluated on the actual bra rather than the number and letter alone.
When Should You Recheck Your Bra Size?
Your measurements can change over time, so it is useful to reassess your fit when your current bras start feeling noticeably different. Weight changes, pregnancy, breastfeeding, aging and other body changes can affect measurements and comfort.
Bra Size Calculator FAQs
How do I calculate my bra size?
Measure around your ribcage underneath your bust and around the fullest part of your bust. Enter both measurements into the calculator to get an estimated starting size.
What measurements do I need to find my size?
You need an underbust measurement and a full-bust measurement. A soft measuring tape is the easiest tool to use at home.
Should the measuring tape be tight?
The tape should be secure and level. Avoid pulling it so tightly that it compresses your body or breast tissue.
What is the difference between band size and cup size?
The band number represents the measurement around your torso underneath your bust. The cup letter represents the relative difference between the bust and band measurements.
What is a sister size?
A sister size changes the band and cup letters in opposite directions while aiming for a similar cup volume. It can be useful when your current band feels too loose or too tight.
Why does the same bra size fit differently in different brands?
Brands can use different sizing charts, cup shapes, materials, wire designs and construction. Always check the manufacturer’s chart when possible.
How should the band of a bra fit?
It should feel snug and supportive while remaining comfortable. It should sit relatively level around your torso instead of riding upward. :contentReference[oaicite:5]{index=5}
How should bra cups fit?
The cups should comfortably contain the breast tissue without obvious spilling or significant gaping. The correct cup shape is also important, so changing styles can sometimes improve fit even when the measured size remains similar. :contentReference[oaicite:6]{index=6}
Can I use centimeters instead of inches?
Yes. Select centimeters in the calculator and enter both measurements in centimeters. The calculator converts them internally before estimating your size.
Can I use this calculator for shopping online?
Yes. Use the result as a starting point, then compare it with the size chart provided by the store or brand you are buying from.
Is the calculated size guaranteed to fit?
No. A measurement-based calculator provides an estimate. Bra design, breast shape, materials and brand-specific sizing can affect the final fit.
Note: This calculator is intended for general sizing guidance and educational purposes. It does not replace professional fitting advice or an individual manufacturer’s size chart.