Bra Size Calculator

What Is a Bra Size Calculator?

A bra size calculator is an online tool that estimates your bra size using your bust and underbust measurements. It calculates a recommended band and cup size and can show equivalent sizes for different countries, making it easier to understand your measurements and compare bra sizes when shopping.

Because sizing can vary between brands, bra styles, and countries, the calculated size should be treated as a starting point rather than a guaranteed fit.

How to Use the Bra Size Calculator

Using the bra measurement calculator takes only two measurements. For the best estimate, use a flexible measuring tape and keep it level around your body.

Step 1: Enter Your Bust Size

Measure around the fullest part of your bust and enter the measurement in the Bust Size field.

Select the appropriate unit, such as centimeters or inches.

Step 2: Enter Your Band Size

Measure around your rib cage directly beneath your bust. Enter this measurement in the Band Size field.

Again, select the unit that matches your measurement.

Step 3: Click Calculate

Click the Calculate button. The bra calculator processes your bust and band measurements to estimate your band and cup size.

Step 4: Check Your Recommended Size

Your results show a recommended bra size along with equivalent or alternative sizing for supported regions, including:

• Recommended US/CA size

• UK size

• US/CA Underbust +4 size

• UK Underbust +4 size

• EU (EN 13402) size

• FR/BE/ES size

• India size

• Australia/New Zealand size

Use these results as a starting point when choosing a bra. Individual brands may use slightly different sizing charts.

How to Measure Bra Size Correctly

Accurate bra measurement starts with two numbers: your bust measurement and your underbust or band measurement.

A soft measuring tape works best. Stand naturally and avoid pulling the tape excessively tight.

How to Measure Bust Size

Wrap the measuring tape around the fullest part of your bust.

Make sure the tape:

• runs straight and level around your body

• sits comfortably against the bust

• does not compress the breast tissue

• is neither hanging loose nor pulled excessively tight

Record the measurement in inches or centimeters.

This is your bust measurement.

How to Measure Band Size

Wrap the measuring tape around your rib cage directly underneath your bust, close to where the bottom of a bra band normally sits.

Keep the tape:

• parallel to the floor

• comfortably snug

• flat against your body

• free from twists

Record the measurement.

This is your underbust measurement, which the bra calculator uses to determine the appropriate band size according to its sizing method.

How to Calculate Bra Size

Bra size combines two parts:

$Band Size + Cup Size$

For example:

$34C$

Here, 34 represents the band size and C represents the cup.

The calculation begins with your bust and underbust measurements. The calculator determines an appropriate band size and then uses the difference between the relevant bust and band measurements to determine the cup.

Bra Cup Size Formula

A simplified way to understand the cup calculation is:

$34C$

The resulting difference is mapped to a cup letter according to the sizing system being used.

However, bra sizing is not completely universal. Cup lettering and band conversions can vary between US, UK, European, and manufacturer-specific sizing systems.

That is why the bra size calculator performs the sizing and regional conversion automatically rather than requiring you to manually interpret the measurements.

How to Measure Cup Size

Your cup size is not simply a standalone measurement. It represents the relationship between the bust measurement and band size.

In general, a larger difference between the bust and band corresponds to a larger cup designation within the sizing system.

For example, when working in inches, a basic sizing sequence may progress approximately like this:

After this point, cup naming can differ significantly between sizing systems and brands. For example, UK and US sizing do not always use the same cup-letter progression.

For this reason, use the table as an explanation of how cup sizing works, rather than assuming it is a universal bra size chart.

Bra Size Calculation Example

Suppose your measurements are:

Bust Size: 95 cm
Band Size: 85 cm

After entering these measurements into the calculator, the displayed recommended US/CA result is:

34C

The calculator also provides regional and alternative sizing results:

This example highlights an important point: the same body measurements may be represented differently across regional bra-sizing systems.

It does not necessarily mean your body or cup volume has changed. The labeling convention has changed.

Why Bra Sizes Can Differ Between Countries

Bra sizing is not standardized globally.

A person can therefore see different numbers or cup letters for US, UK, European, French, or Australian sizing even though their actual body measurements have not changed.

The differences can involve:

• band-number conventions

• cup-letter sequences

• regional conversion methods

• manufacturer sizing systems

• bra construction and style

Cup letters are also related to band size rather than representing a fixed breast volume on their own. For example, changing the band while keeping the same cup letter can change the actual cup volume.

That is why an international bra size chart or converter is useful when purchasing bras from brands that use another country's sizing system.

Bra Size Converter

Already know your bra size? You don't need to measure yourself again.

Select the Bra Size Converter tab to compare your known size across the sizing systems supported by the calculator.

How to Use the Bra Size Converter

Step 1: Select your location

Choose the sizing system you already know, such as US/CA.

Step 2: Select your size

Choose your current band size from the Size dropdown.

Step 3: Select your cup

Choose your known cup size.

Step 4: Click Convert

The converter displays equivalent sizes across the supported regional systems.

For example, when US/CA 28AA is selected, the converter shown by the tool provides corresponding references for UK, EU (EN 13402), FR/BE/ES, Australia/New Zealand, Underbust +4 sizing, and UK dress code sizing.

This feature is especially helpful when shopping from an international brand or comparing a familiar bra size with another country's bra size chart.

Remember that conversions provide a useful starting point. Fit can still vary by brand, fabric, bra shape, and construction.

Bra Size Chart

A bra size chart helps you understand how band and cup sizes relate to each other. However, there is no single chart that guarantees the same fit across every brand or country.

The band number represents the sizing system's band measurement, while the cup letter represents cup volume relative to that band size. This is why a C cup on one band size does not have exactly the same volume as a C cup on another band size.

A simple US-style cup progression can be understood as follows:

After D, cup naming can vary significantly between US, UK, European, and individual brand sizing systems. Always use the sizing system required by the brand you are buying.

International Bra Size Differences

Bra size labels can change when you shop internationally.

For example, US/CA, UK, EU, FR/BE/ES, India, and Australia/New Zealand may use different band numbers or cup sequences for comparable measurements.

That is why the Bra Size Calculator provides regional conversions instead of requiring you to manually convert each size.

When buying a bra from another country, use the Bra Size Converter as a starting point and compare the result with the manufacturer's own size chart before ordering.

How to Know If Your Bra Fits Correctly

Getting a result from a bra calculator is only the first step. Your actual bra should also feel secure and comfortable when worn.

Here are some important fit checks.

Band Stays Level

The band should sit approximately level around your body rather than noticeably riding upward at the back.

It should feel secure without being painfully tight.

Cups Fit Smoothly

Your breast tissue should sit comfortably inside the cups.

Visible spilling over the top or sides can indicate that the cups are too small or that the style is not suitable for your shape.

On the other hand, noticeable gaping or wrinkling may indicate that the cup is too large or that the cup shape does not match your breast shape.

Center Gore Sits Properly

On many underwired bras, the center section between the cups, known as the center gore, should sit close to the chest.

However, bra construction and individual anatomy can affect how the gore sits.

Straps Stay in Place

Bra straps should remain comfortably on your shoulders without repeatedly slipping or digging deeply into the skin.

Avoid relying on very tight straps to compensate for a loose band.

Underwire Surrounds the Breast Tissue

For an underwired bra, the wire should generally sit around the breast tissue rather than resting on or digging into it.

Remember that two bras carrying the same size label can still fit differently because of differences in cup shape, fabric, wire width, construction, and brand sizing.

What Are Sister Bra Sizes?

Sister sizes are bra sizes with different band and cup labels but approximately similar cup volumes.

When you move to a smaller band, you generally move up one cup designation. When you move to a larger band, you generally move down one cup designation.

For example, in a sizing system where the cup progression follows this pattern:

$32D \leftrightarrow 34C \leftrightarrow 36B$

These are commonly considered sister sizes.

So, if a 34C has cups that fit well but the band feels too tight, trying a 36B may provide a similar cup volume with a larger band.

If the 34C band feels too loose, a 32D may be worth trying.

Sister sizing is a fitting technique rather than a guarantee. Moving several band sizes away from your measured size can substantially change the fit and support.

Benefits of Using a Bra Size Calculator

A bra measurement calculator provides a quick starting point when you are unsure which size to try.

Key benefits include:

• estimates your band and cup size from simple measurements

• removes much of the guesswork from manual calculations

• helps you understand the relationship between bust and band measurements

• makes international size comparison easier

• provides a useful starting size for online shopping

• helps you identify nearby sizes worth trying

The biggest advantage is convenience. Instead of manually working through measurement differences and regional sizing systems, the bra calculator organizes the information in one result.

When Should You Measure Your Bra Size?

Consider taking a new bra measurement whenever your existing bras no longer fit the way they used to or you are unsure of your current size.

Re-measuring can be particularly useful when:

• buying new bras

• shopping from an unfamiliar brand

• ordering bras online

• switching to another country's sizing system

• your current band repeatedly rides up

• your cups gape or overflow

• your measurements have changed

• you have not measured yourself for a long time

There is no need to assume your bra size will remain unchanged indefinitely. Rechecking your measurements can give you a better starting point when your current bras stop fitting comfortably.

Who Should Use a Bra Size Calculator?

A cup size calculator or bra calculator can be useful for anyone who wants a quick estimate of their bra size.

It is especially helpful for:

• first-time bra shoppers

• people unsure of their current bra size

• online shoppers

• people comparing international bra sizes

• anyone experiencing fit problems with their current bras

• shoppers changing between brands or sizing systems

• anyone whose body measurements have changed

Even if you already know your size, the Bra Size Converter can be useful when purchasing from international retailers.

Common Bra Measurement Mistakes

Small measurement errors can change the result produced by a bra measurement calculator. Avoid these common mistakes when measuring yourself.

Pulling the Tape Too Tight

A measuring tape that compresses your body can produce an inaccurate measurement.

Keep it snug for the underbust measurement without pulling it painfully tight.

Leaving the Tape Too Loose

A loose measuring tape can add unnecessary inches or centimeters to your measurement.

Make sure the tape rests against your body.

Measuring at an Angle

The measuring tape should stay level around your body. If it slopes significantly upward or downward, your measurement may be incorrect.

Measuring the Wrong Part of the Bust

Take the bust measurement around the fullest part of your bust, rather than measuring too high or too low.

Confusing Bust and Band Measurements

These measurements serve different purposes.

Bust measurement: around the fullest part of your bust.

Band/underbust measurement: around your rib cage directly beneath the bust.

Make sure you enter each measurement into the correct calculator field.

Mixing Inches and Centimeters

Always check the selected unit before clicking Calculate.

Entering a centimeter measurement while inches are selected or the reverse will produce an incorrect result.

Assuming Every Brand Fits the Same

A calculated 34C, for example, does not mean every 34C bra will fit identically.

Fabric stretch, cup depth, wire shape, padding, bra style, and manufacturer sizing can all affect fit.

Tips for a More Accurate Bra Size Estimate

Follow these simple practices when using the bra size calculator:

Use a soft measuring tape: A flexible tape follows the body's shape more accurately than a rigid ruler.

Keep the tape level: Check that it remains approximately parallel to the floor around your body.

Measure carefully: If you get noticeably different measurements, repeat the process and check the tape position.

Check your units: Make sure centimeters or inches are selected correctly before calculating.

Stand naturally: Avoid deliberately expanding your chest or holding your breath while measuring.

Use the result as a starting point: Try the recommended size and nearby sizes when possible.

Check the manufacturer's chart: Brand-specific sizing guidance can be especially important when shopping online.

Consider sister sizes: If the cup volume feels suitable but the band does not, an appropriate sister size may provide a better fit.

Final Takeaway

Finding your bra size starts with accurate bust and underbust measurements. The Bra Size Calculator makes this easier by using those measurements to estimate your band and cup size and display relevant international sizing equivalents.

For the best results, measure carefully, select the correct units, and treat the calculated size as a starting point for fitting. Bra sizing can vary between brands, countries, materials, and styles, so always check how the actual bra fits and compare the manufacturer's size chart when necessary.

Helpful Resources

• Professional Guide to Finding the Perfect Bra Fit

• International Bra Size Conversion Chart

Pro Tips

• Measure yourself while wearing a well-fitting, non-padded bra for the most accurate results.

• Take measurements at the end of the day when your body is at its largest.

• Consider trying on different sizes and styles to find the most comfortable fit.

• Remember that bra sizes can vary between brands, so use the calculator as a starting point and adjust as needed.

• Regularly re-measure yourself, as your body can change over time due to factors like weight fluctuations, pregnancy, or aging.