Bra Size Calculator
Free bra size calculator: enter your underbust and bust to get your band and cup, with US, UK, EU, French and Australian conversions and sister sizes. Modern or +4 method, inches or cm.
https://hexacalculator.com/calculators/daily/general/bra-size-calculator
Daily
General
Bra Size Calculator
Free bra size calculator: enter your underbust and bust to get your band and cup, with US, UK, EU, French and Australian conversions and sister sizes. Modern or +4 method, inches or cm.
Bra Size Calculator
What would you like to do?
Your measurements
Measure in inches or centimetres (switch the unit on each field). Wear a soft, non-padded bra for the truest numbers.
Your bra size
Enter your underbust and bust measurements to see your bra size.
A bra size calculator converts two body measurements into a size. Enter the under bust measurement, measured just below your breast and the bust measurement at its fullest point, loosely measured. The calculator will then calculate the size and convert it to US, UK, EU, French and Australian sizes with related sizes shown.
How to measure your bra size:
Wear a soft non-padded bra so that your breasts are in their natural shape. Underwire bras or thick padded bras will both distort the measurements and sports bras can affect the measurements.
Measure your underbust circumference. Place the tape measure around your torso just below your breast and run it all the way around so that it is snug against your body and running parallel to the floor.
Next measure your bust size. Place the tape measure around the fullest part of your chest and pull it slightly snug while making sure that it stays horizontal. Round each measurement to the nearest quarter inch or half centimeter.
This is how you calculate your under-bust circumference and cup size.
The band size is determined by the circumference of your bust below the breast while the cup size depends on how much larger the breast is in comparison to the circumference of your bust below the breast.
There are generally two methods for calculating a band size, and this tool offers both. The modern method rounds the underbust circumference to the nearest even inch, so an underbust circumference of 34 inches results in a band size of 34. Most brands and bra fitters currently use this method. The older "+4" method adds four inches for even underbust circumferences and five inches for odd underbust circumferences. This generally results in looser band sizes and smaller cup sizes.
If the underbust circumference becomes larger there is a guide that reduces by an addition of 4 inches incrementally. If you are referring to older size charts it helps to note this.
Underbust (in) | How to get the band |
|---|---|
26 – 32 | add 4 if even, 5 if odd |
33 – 38 | add 2 if even, 3 if odd |
39 and up | add 0 if even, 1 if odd |
The cup size is determined by the difference between your bust and underbust measurement with each inch of difference corresponding to a cup size. So if your underbust measures 34 and your bust measures 38 inches, then the difference is four inches which corresponds to a D-cup size. The full size would be 34D.
Bust − band (in) | US cup | UK / AU cup | EU cup |
|---|---|---|---|
0 | AA | AA | AA |
1 | A | A | A |
2 | B | B | B |
3 | C | C | C |
4 | D | D | D |
5 | DD / E | DD | E |
6 | DDD / F | E | F |
7 | DDDD / G | F | G |
8 | H | FF | H |
Conversion of sizes by countries.
The letter designations on bra sizes are usually the same for different countries, but the numbers for half-sizes can vary greatly. Even with the same bust circumference, there can be completely different size indications depending on the country of origin of the bra. This is why a direct conversion of sizes often does not work.
US / UK | EU (EN 13402) | France / BE / ES | Australia / NZ |
|---|---|---|---|
30 | 65 | 80 | 8 |
32 | 70 | 85 | 10 |
34 | 75 | 90 | 12 |
36 | 80 | 95 | 14 |
38 | 85 | 100 | 16 |
40 | 90 | 105 | 18 |
Sister sizes
Sister sizes keep the cup size but change the band size. If you go down one band size and up one cup size (e.g. from 34D to 32DD), your band will be tighter. Conversely, if you go up one band size and down one cup size (e.g. from 34D to 36C), your band will be looser. If the cups fit but the band is either riding up or uncomfortable tight, try a sister size first before just changing the letter of the cup size.
How to get a bra that fits properly
As the bottom part of the bra provides most of the support it should be close to your body and run horizontally. It is recommended that you start by fastening the bra with the outermost hook as the bottom can stretch over time. The cups should completely enclose your breast without bulging outwards or upwards on the sides. Also, they shouldn't stand up or wrinkle. The straps should be firm but provide only about a tenth of the support so that they don't cut into your skin or slip off.
Surveys show that many people wear bras that are not the right size for them. A common mistake is to have a band that's too big and cups that are too small. The methods of data collection can vary, so this figure should not be overestimated. However, there are real trends in this area, and getting the right fit can solve many of these problems.
Breast shape and daily changes
Even if the measurements are the same, the fit required can vary depending on breast shape (e.g. full top, sagging, outgrown, asymmetrical) and also what cut fits best may differ. About 40 percent of people have a significant size difference between their breasts. Fit the bra to the larger side and adjust the band of the smaller side accordingly.
Your size is not fixed. As your size can change due to weight fluctuations, pregnancy, breastfeeding, hormones and age, you should get yourself measured every six to twelve months or when your favourite bra no longer fits.
How to use the calculator:
Stay on the Find My Size mode, enter your bust and cup size and check out the sizes listed and conversion results on the right. Switch between inches and centimeters for individual measurements if needed. If you already know a US or UK size, switch to the Conversion Mode, select your sub-size and cup size to find the corresponding size in other systems.
While this calculator will give you a good starting size, it does not guarantee a perfect fit. As brands and styles vary, be sure to try on the calculated size and adjust the band, cup or style as needed for optimal comfort.
Frequently asked questions
- How is bra size calculated?
A bra size is made up of two parts. The number for the bottom cup size is determined by your bust (underbust) measurement, while the letter for the cup size is based on the difference between your bust and bottom cup size. For every inch of difference between your bust and bottom cup size, your cup size goes up one level. So, one inch equals A, two inches equals B, three inches equals C, and four inches equals D. So if you have a 34 bottom cup and your bust is four inches larger, then your size would be 34D.
- How to measure your bra size?
Wear a soft, unlined bra so your breasts are in their natural shape. Start by measuring the underbust. Wrap the tape measure around your torso just below your bust and bring it all the way back to meet at the front of your body, making sure it is snug against you and parallel with the floor. Next, measure your bust. Wrap the tape measure loosely around the fullest part of your bust and hold it horizontally. Round each measurement up to the nearest quarter inch or half centimeter, then enter both measurements. Take a new measurement every six to twelve months, or if you've gained weight or had a baby.
- What is the difference between the Modern Method and the +4 method?
Both methods are used to convert your bust size into a bottom cup size. The modern method rounds up the bust size to the nearest even inch. This is currently the recommended method by most brands and lingerie experts. The older "+4" method adds four inches to an even bust size, and five inches to an odd bust size. The "+4" method usually results in looser bottom cup sizes and smaller cup sizes, often resulting in the typical "too big bottom cups, too small cups" mistake. A calculator will show both results so you can compare them and try them on accordingly.
- What are sister sizes?
Sister sizes have the same amount of padding but differ in band size. Whether you reduce your band size by one and increase your cup size by one (e.g. from 34D to 32DD), or increase your band size by one and decrease your cup size by one (e.g. from 34D to 36C), the amount of padding remains essentially the same, but the fit of the bra changes. If you have a good fit in terms of cups but the band rides up or pinches, switching to a sister size can solve that problem without compromising the fit of the cups themselves.
- How do I convert my bra size to EU, French or Australian?
A US or UK 34 is a EU size 75 (EN 13402), French, Belgian and Spanish 90 and Australian/New Zealand 12. When you enter your measurements or activate the conversion mode and give a known size all corresponding sizes for the different systems will be shown in the results area at the same time.
- Why do bra sizes differ between brands?
Because there are no uniform standards for cup sizes and bras, the fit of different brands can be different even if they both have the same size (34B). Even people with the same height may find that one style fits as a 34B while another style feels like a 34C. A common reason is that many people wear clothing in a size that doesn't fit them perfectly. Use the given size as a starting point and adjust the cup or band to feel right for you. Consider using sister sizes for more precise fitting if necessary.
Related calculators
Disclaimer: This calculator is provided for general informational and educational purposes only. Our calculators are under active development, and results may be inaccurate, incomplete, or unsuitable for your situation. Always verify the figures independently and seek advice from a qualified professional before relying on them. We make no warranties and accept no liability for any loss or decision arising from use of this tool.
References
- A Bra That Fits — Calculator & methodology
Community-maintained fitting method based on multiple underbust and bust measurements.
- Wikipedia — EN 13402 (bra sizes)
International band and cup systems, the difference-to-cup rule, and the EN 13402 standard.