Bra Size Calculator

Bra Size Calculator-Use our free Bra Size Calculator to estimate your bra size from your underbust and bust measurements. Learn how to measure yourself and understand band and cup sizes.Explore our complete collection of Golf Handicap Calculator , Sleep Calculator,Dividend Calculator,Shoe Size Conversion, Tip Calculator,conversion, and everyday calculators at CalculatorGuides.com to find the right tool for your needs.

A Bra Size Calculator helps you estimate your bra size using two simple measurements:

• Underbust measurement
• Bust measurement

The calculator uses the difference between these measurements to estimate your band size and cup size.

Finding the right bra size can make a big difference in comfort and fit. However, bra sizing is not completely standardized, so the same size can fit differently between brands and styles.

Use the calculator as a starting point, then check the brand’s own size chart whenever possible.

Important: Bra sizes are estimates. Different brands, countries, fabrics, cup shapes, and bra styles can fit differently even when the label shows the same size.

What Is a Bra Size Calculator?

A Bra Size Calculator estimates your bra size from your body measurements.

A typical calculation uses:

Band size + Cup size = Bra size

For example:

34 + C = 34C

The band number represents the approximate size around your torso, while the cup letter represents the difference between your bust and band measurements.

How to Measure Your Bra Size

You usually need two measurements.

1. Underbust Measurement

Measure around your rib cage directly underneath your breasts.

Keep the measuring tape:

• Level around your body
• Comfortable
• Snug but not painfully tight

2. Bust Measurement

Measure around the fullest part of your bust.

Keep the tape:

• Level
• Not too tight
• Flat against your body

Do not pull the tape tightly enough to compress your bust.

How to Measure Underbust

Stand naturally and breathe normally.

Place the measuring tape directly underneath your breasts and around your rib cage.

Record the measurement in:

inches or centimeters

For example:

Underbust = 31 inches

This measurement helps determine the band size.

How to Measure Bust

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

Keep the tape horizontal around your body.

For example:

Bust = 35 inches

If your underbust is:

31 inches

the difference is:

35 − 31 = 4 inches

That difference is used to estimate the cup size.

Bra Size Formula

A simplified bra-size calculation works like this:

Step 1

Measure your underbust.

Step 2

Determine the appropriate band size according to the sizing system being used.

Step 3

Measure your bust.

Step 4

Calculate:

Cup Difference = Bust Measurement − Band Measurement

Step 5

Use the difference to estimate the cup letter.

Because sizing systems differ, the exact conversion should follow the relevant country’s or brand’s size chart.

Simple Cup Size Chart

A commonly used approximate US/UK-style chart is:

Bust-to-Band Difference	Approx. Cup
1 inch	A
2 inches	B
3 inches	C
4 inches	D
5 inches	DD/E
6 inches	DDD/F
7 inches	G
8 inches	H

This is only a general guide. Brand sizing can vary.

Bra Size Example

Suppose your measurements are:

Underbust: 32 inches

Bust: 36 inches

Difference:

36 − 32 = 4 inches

A simplified chart would suggest approximately:

32D

Your actual best-fitting size may be different depending on the brand and bra style.

Another Bra Size Example

Suppose:

Underbust:

34 inches

Bust:

37 inches

Difference:

3 inches

A basic US/UK-style calculation may suggest:

34C

Again, use the manufacturer’s chart when purchasing.

Bra Band Size

The band is the number in a bra size.

Examples:

• 30B
• 32C
• 34D
• 36DD
• 38C

The band fits around your rib cage.

It provides much of the support in a well-fitting bra.

Bra Cup Size

The cup is represented by a letter.

Examples:

• A
• B
• C
• D
• DD
• E
• F

The cup size is based on the difference between the bust and band measurements.

One important point is that cup letters are not absolute sizes.

For example, a 32D and a 36D do not have the same cup volume.

Why Cup Size Changes With Band Size

Cup volume is related to the band size.

For example:

32D

and

36D

have the same letter but different overall cup volumes.

This is why it is better to think of a bra size as a complete combination of:

Band + Cup

rather than treating the cup letter by itself as a fixed measurement.

Sister Sizes

Sister sizes are bra sizes with similar cup volume but different band measurements.

For example, approximate sister-size relationships can look like:

34C → 32D → 36B

The cup volume is similar, while the band changes.

This can be useful when the cup seems right but the band feels too loose or too tight.

How Sister Sizes Work

If the band feels too loose:

Go down one band size and up one cup letter.

Example:

34C → 32D

If the band feels too tight:

Go up one band size and down one cup letter.

Example:

34C → 36B

These are approximate sister sizes and should be checked against the specific brand’s sizing system.

US Bra Size Chart

A commonly used US-style size progression includes:

30A, 30B, 30C, 30D, 30DD

32A, 32B, 32C, 32D, 32DD

34A, 34B, 34C, 34D, 34DD

36A, 36B, 36C, 36D, 36DD

The exact size range and letter sequence vary between manufacturers.

UK Bra Size Chart

UK bra sizing commonly uses:

A, B, C, D, DD, E, F, FF, G, GG, H

This is one reason a UK size may not directly match a US size with the same letter.

For example, UK and US cup naming becomes increasingly different at larger cup sizes.

Always check which country’s sizing system a retailer uses.

US vs UK Bra Sizes

US and UK bra sizing are similar at some sizes but diverge at others.

For example, a size such as:

34DD

can represent different sizing conventions depending on whether the chart is US or UK.

When shopping internationally, do not rely only on the label.

Use the brand’s conversion chart.

EU Bra Sizes

European bra sizing commonly uses centimeters for the band number.

For example, a European bra may be labeled:

70C

or:

75D

The number does not directly correspond to the US/UK band number.

Therefore:

EU 75

should not simply be read as:

US 75

The sizing system must be identified first.

International Bra Size Conversion

A general conversion may look like this:

US	UK	EU Approx.
32C	32C	70C
34C	34C	75C
36C	36C	80C
38C	38C	85C

Cup conversions can become more complicated at larger sizes.

Brand-specific charts should always take priority.

Bra Size in India

Bra sizing in India varies by brand and retailer.

Many Indian brands use band-and-cup labels such as:

32B

34C

36D

However, the measurement method and conversion can differ.

When shopping in India, measure your bust and underbust and compare them with the individual brand’s size chart rather than assuming every brand follows exactly the same measurements.

Bra Size in Centimeters

If you measure in centimeters, use the size chart designed for centimeter measurements.

For example:

Underbust = 75 cm

Bust = 90 cm

The correct bra size depends on the sizing system and brand.

Do not simply convert centimeters to inches and assume the same size will fit.

How Should a Bra Band Fit?

A properly fitting band should feel:

• Snug
• Comfortable
• Level around your body
• Secure without painful pressure

The band should not ride significantly upward at the back.

A new bra is generally expected to fit comfortably on a relatively looser hook setting so there is room to tighten it as the elastic wears.

How Should the Cups Fit?

The cups should generally:

• Contain the breast tissue comfortably
• Not create excessive spillage
• Not have large empty areas
• Sit smoothly against the body

However, cup shape matters.

A bra can be technically the “right” size but still fit poorly if the cup shape does not suit your breast shape.

Signs Your Bra May Be Too Small

Possible signs include:

• Breast tissue spilling over the top
• Spilling near the sides
• Underwire sitting on breast tissue
• Cups cutting into the skin
• Center section not sitting comfortably
• Band feeling excessively tight

These signs can indicate that you need a different size or style.

Signs Your Bra May Be Too Large

Possible signs include:

• Cups have significant empty space
• Fabric wrinkles excessively
• Straps constantly fall
• Band rides upward
• Cups do not stay in position

Again, the issue may be the size, the bra shape, or both.

Why Bra Straps Should Not Carry All the Support

The band generally provides much of the support.

If the straps are doing most of the work, the band may be too loose or the fit may need adjustment.

Straps should be comfortable and secure without digging into the shoulders.

Bra Size and Different Styles

Your preferred size can sometimes change between styles.

For example:

• T-shirt bra
• Push-up bra
• Sports bra
• Balconette bra
• Plunge bra
• Wireless bra
• Full-coverage bra

These designs use different cup shapes and construction.

A size that fits well in one style may not fit exactly the same way in another.

Sports Bra Size

Sports bras can use different sizing systems.

Some use:

• Band and cup sizes
• XS/S/M/L/XL
• Numeric sizing
• Brand-specific measurements

For a sports bra, check the manufacturer’s chart and consider both bust and underbust measurements.

Nursing Bra Size

During pregnancy and breastfeeding, breast size and shape can change.

A bra that fits at one stage may not fit the same way later.

When choosing a nursing bra, consider:

• Current measurements
• Expected changes
• Adjustable features
• Cup accessibility
• Band adjustability
• Comfort

A calculator can provide a starting estimate, but fitting can be especially important during this period.

Bra Size and Weight Changes

Body measurements can change when weight changes.

If your underbust or bust measurement changes significantly, your bra size may also change.

It is useful to remeasure rather than automatically buying the same size.

Bra Size Calculator Formula Summary

Cup Difference

Cup Difference = Bust Measurement − Band Measurement

General Cup Guide

1 inch → A

2 inches → B

3 inches → C

4 inches → D

5 inches → DD/E

This is a simplified guide and should not replace a brand-specific size chart.

How to Use the Bra Size Calculator

Step 1: Measure Your Underbust

Measure snugly around your rib cage underneath your breasts.

Step 2: Enter the Measurement

Enter your underbust measurement in inches or centimeters.

Step 3: Measure Your Bust

Measure around the fullest part of your bust.

Step 4: Enter Your Bust Measurement

Use the same measurement unit.

Step 5: Select the Sizing System

Choose the relevant system, such as:

• US
• UK
• EU
• India

Step 6: Calculate

The calculator provides an estimated bra size.

Step 7: Check the Brand Chart

Use the manufacturer’s measurements before purchasing.

Common Bra Size Calculation Mistakes

Measuring Over Thick Clothing

Clothing can add measurement and reduce accuracy.

Pulling the Tape Too Tight

The tape should not compress your body.

Measuring Only Your Bust

Both underbust and bust measurements are important.

Using the Wrong Country’s Chart

US, UK, and EU sizing systems differ.

Assuming Cup Letters Are Universal

A C cup does not represent the same absolute volume at every band size.

Ignoring Bra Shape

Different styles can fit differently even in the same labeled size.

Frequently Asked Questions

What is a Bra Size Calculator?

A Bra Size Calculator estimates your bra band and cup size from your underbust and bust measurements.

How do I measure my bra size?

Measure your underbust around your rib cage and your bust around the fullest part. Then compare both measurements with the appropriate size chart.

Should I measure over clothing?

For the most useful measurement, use minimal clothing or thin clothing that does not add significant thickness.

Should I measure both breasts?

The measurement is taken around your full bust rather than measuring each breast separately.

What is band size?

Band size is the number in a bra size, such as 34 in 34C.

What is cup size?

Cup size is represented by the letter, such as C in 34C.

Does cup size stay the same across band sizes?

No. Cup volume changes with band size.

What are sister sizes?

Sister sizes are sizes with similar cup volume but different band and cup combinations.

Why does the same bra size fit differently between brands?

Brands can use different measurements, materials, cup shapes, and sizing standards.

Is a 34C the same everywhere?

No. A labeled 34C can fit differently depending on the brand and sizing system.

Can my bra size change?

Yes. Body measurements can change with weight changes, pregnancy, breastfeeding, aging, and other normal changes.

Is a sports bra sized the same as a regular bra?

Not always. Sports bras may use band-and-cup sizes or general sizes such as S, M, and L.

Should the bra band ride up?

A band that rides noticeably upward can indicate that the band is too loose or the fit needs adjustment.

Should bra cups have wrinkles?

Significant empty space or wrinkling can indicate that the cup shape or size is not right, although some styles naturally have different construction.

Is the Bra Size Calculator accurate?

It can provide a useful starting estimate, but no calculator can guarantee the perfect fit across every brand and style.

Is the Bra Size Calculator free?

Yes. The CalculatorGuides.com Bra Size Calculator is free to use.

Bra Size Calculator – Important Things to Remember

For a better estimate:

• Measure your underbust accurately.
• Measure the fullest part of your bust.
• Keep the measuring tape level.
• Do not pull it excessively tight.
• Measure both sides of your body as needed.
• Select the correct sizing system.
• Check the brand’s own size chart.
• Consider cup shape and width.
• Try the bra on when possible.

Your calculated size is a starting point, not a guarantee of fit.

Conclusion

A Bra Size Calculator provides a simple way to estimate your bra size using your underbust and bust measurements.

The basic idea is to determine the appropriate band size and then use the difference between the bust and band measurements to estimate the cup size.

However, bra sizing is not completely standardized. US, UK, EU, Indian, and other sizing systems can differ, and even two brands using the same label may have different fits.

For the best result, use the calculator to find a starting size, then compare your measurements with the specific brand’s official size chart. The style of bra, cup shape, band construction, and your individual body shape can all affect how comfortable the final fit feels.

Use the CalculatorGuides.com Bra Size Calculator to estimate your size quickly and make online bra shopping easier.