The idea of a bra size calculator or bra size chart can be really appealing. Just enter in some measurements, and voila! It will calculate bra sizes for you. But do they really work? How do you find a good bra size calculator? In this article, we’ll discuss how bra size calculators and bra size charts work, provide our own reliable bra size chart, and explain how to use it! We also include a US-UK bra size converter.
What’s a Bra Size Calculator? Do They Work?
A bra size calculator or bra size chart is designed to simply calculate bra sizes for you. For bra calculators, you usually enter in your underbust and bust measurement, hit enter, and get back a bra size. For bra size charts, you usually find your underbust measurement on one side, your bust measurement on the other, and find the size in the chart. Sounds simple enough, right?
Unfortunately, it’s pretty difficult for a bra size calculator or bust size chart to give an accurate measurement all the time. This is for a few reasons. First, not every brand sizes their bras exactly the same. This is doubly a problem because there are so many brand-specific bra size calculators and bra size charts out there. These charts might tell you the correct size in one brand, but they certainly won’t tell you the correct size in other brands. You would think that in this modern era bra sizing would be more standardized, but alas, it’s not.
There’s another, more salient reason why bra size calculators and bra size charts often don’t work. Simply put, not every body is the same. One woman with a 31-inch underbust measurement may wear a 30” band, while another woman may wear a 32 or even a 34.
With all that said, a bra size calculator or breast size chart can be a useful tool, provided you choose a reliable one and use it correctly. See our reliable bra size chart in the next section.
Our Best Bra Size Chart
Looking for a reliable bra size calculator or bra size chart? Look no further than our bra-size chart, presented below!
American Bra Sizes Chart
|Underbust (down) / Bust (across)||28.6
|Underbust (down) / bust (across)||42.5-43.4||43.5-44.4||44.5-45.4||45.5-46.4||46.5-47.4||47.5-48.4||48.5-49.4||49.5-50.4||50.5-51.4||51.5-52.4||52.5-53.4||53.5-54.4||54.5-55.4||55.5-56.4||56.5-57.4||57.5-58.4|
Note: DD is interchangeable with E and DDD is interchangeable with F.
It goes without saying that a bra size calculator or bust size chart is of no use to you if it calculates bra sizes incorrectly. So how do you know that our chart is reliable?
It uses your rounded underbust measurement as your band measurement.
Bra band sizes go in 2-inch increments. So, 28 inches, 30 inches, 32 inches, and so on. Your band size should essentially be your underbust measurement (more on that in the next section) rounded to the nearest inch. If it’s an odd number, you’ll add one inch. So, a 31.2 underbust is a 32-inch band. That’s how our bra size chart works.
Why am I calling attention to this? Well, some bra size charts or calculators may add four inches (or some other number) to the underbust measurement to get your band size, which is incorrect. This is because when bras were first designed, they were made of pretty stiff fabric—so without the extra four inches you wouldn’t be able to breathe! But now that bras are made out of stretchy, elasticated fabrics, this isn’t necessary. A bra size calculator or bra size chart that adds several inches to your underbust size to give you your band size will consistently give results that are too loose in the underbust and too small in the cups. (See this chart from La Senza, which bizarrely adds up to six inches to the underbust to give band size!)
It calculates your cup size correctly.
Cup size expresses the approximate difference between your bust and your band, with a 1 inch difference corresponding to an A cup, a 2-inch difference to a B cup, and so on. Thus, a correct cup size measurement subtracts your band measurement from your bust measurement to reach cup size.
Lots of bra size calculators and bra size charts do not do this correctly! Many calculators (like this one from Linda’s online and this one from calculator.net) make the critical mistake of first giving a band size that’s your underbust measurement +4, and then giving you a cup size that’s the difference between your bust and your actual underbust.
For example, when I entered in an underbust measurement of 30” and a bust measurement of 34” in the calculator.net calculator, it gave me back a size of 34D! This is both a band size and a cup size that are much too large. The band size should be 30 and the cup size should be D. But a 30D cup is equivalent to a 34A in terms of cup volume! That’s just one example of why it’s critical to use a bra cup size calculator or chart like ours that determines cup size by subtracting the band measurement from the bust, and not the underbust measurement from the bust.
It’s easy to use!
We provide a measurement range for each band and cup size so you don’t have to worry about rounding—we did it for you!
So, once you’ve taken your underbust and bust measurements (see the next section if you don’t know how to do that), find the row with your underbust measurement along the left side and then the column where your bust measurement falls along the top. Where the row and column meet is your size!
Also, cells along the same diagonal are sister sizes. A sister size is a bra with a different band and cup size but the same cup volume. So, a 34A is sister sizes with a 32B is sister sizes with a 30C is sister sizes with a 28D. This is useful information if for whatever reason you try on a bra in your usual size and the band is unusually tight or loose. (This can happen due to pesky brand variation!) Then you can switch band sizes while keeping cup volume the same.
How to Use a Bra Size Calculator
Here’s how to take your measurements for the purposes of using a bra size calculator or bra size chart, and how to use the size the calculator or chart gives you to find the right bra!
Step 1: Measure Underbust
Once you’ve found the bra size calculator or breast size chart you’re going to use, you’ll need to measure your underbust.
Bust out a soft measuring tape to get your underbust measurement (pun intended). If you don’t have one, you can use a string and measure it against a yardstick or retractable measuring tape.
To get an an accurate underbust measurement, you need to position the tape measure (or string) right at the base of your breasts, where they meet your ribs. Next, you’ll exhale so you get the smallest measurement. Measure all the way around your torso. The tape should be snug, but not so snug that it digs into you. It’s also critical to keep the tape straight and level all the way around. It can be helpful to look in the mirror to make sure the tape isn’t riding up or down across your back.
Once you’ve got the measurement, note it down.
Step 2: Measure Bust
Once you’ve noted down your underbust measurement, it’s time to measure your bust measurement. You’ll want to take the measurement across the most voluminous part of your breasts. If you have a bra that you think more or less fits (and isn’t too padded), you can take the measurement wearing that bra. In this case, stand up, positioning the measuring tape (or string) across your breasts at about nipple level. You may want to use a mirror to make sure that the tape stays straight around your back. You want to pull tight enough to get an accurate measurement, but not so tight that you start to compress breast tissue. The tape shouldn’t go down into your cleavage, but should go straight across your breasts.
If you don’t feel like you have any bras that fit, you can measure without one one. In this case, you’ll want to bend over parallel to the floor. You want to bend over because there is often breast tissue along the sides of the body that may not be captured in a standing measurement. Bending over ensures that, with the help of gravity, you get all of your breast tissue in your bust measurement. Again, measure at about nipple level, and pull the tape tight enough to get an accurate measurement but not so tight as to compress breast tissue. And make sure the measuring tape is straight in the back and doesn’t ride up or down.
Once you have the bust measurement, note down this number.
Step 3: Enter or Find Measurements
Once you have your measurements, you’ll enter them into the calculator and get a size back. If it’s a chart, you’ll find your underbust measurement along one side and then your bust measurement along the other. The cell in the chart where they meet gives you your size.
If you’ve done the work of selecting the right bra size calculator or bra size chart (like ours!), it really is that easy! However, as we’ve already stated, the result you get back even from a pretty reliable calculator or chart is just a starting place.
Step 4: Use Your Chart Result as a Starting Point
Once you’ve got your starting size courtesy of the bra size calculator or bra size chart, you’ll want to go to the store and try on bras in that size from a few different brands and in a few different styles. If you’re having consistent fit issues, try the following adjustments.
If the band is too tight:
If the band is too tight, go up a band size. If the cups are fine and it’s just the band that’s the issue, you’ll also need to adjust your cup size to keep the cups themselves the same volume in the new band.
For every band size you go up, move down a cup size (so, if you are switching from 32B to a 34, that would be a 34A).
If the band is riding up:
If the band is riding up, it’s probably too loose. If the cups are fine and it’s just the band that’s too loose, you’ll need to adjust your cup size in the new band to keep the volume the same. For every band size you go down, move up a cup size. So if you are moving from a 32B to a 30, your new cup size would be 30C.
If breast tissue is spilling out of the cups:
If breast tissue is spilling out of the cups on the sides or up over the top of the cups, your cups are too small. Same thing if underwire is digging into the side of your boob. Try moving up a cup size while keeping band size the same. If that doesn’t seem to help, the bra style could be the issue; try some different styles.
If cups are puckering:
If the cups are gapping away from the breast at the top, they are too large. Cups should be flush with the surface of the breast. Try moving down a cup size. If that doesn’t work, it may simply be a bra type that doesn’t work well for you. Try some different styles. So if you’re in a demi, try a plunge, and so on.
With a little experimentation, you can use the starting place you get from a reliable bra size calculator or bra size chart to pin down your best bra size!
Bra Size Converter
You might also be looking for a bra size converter to find out your bra size in different brands. The most common bra size conversion that people look for is between US and UK sizes. UK brands are known for having more options for larger busts, so many large-breasted women buy UK brands online. But it’s critical that you figure out your UK size first if you are going to do this! You could look for a dedicated bra size calculator with UK sizing. Or you could just use a US-UK bra size calculator.
US and UK band sizes are the same, so you don’t need to adjust that. However, here’s a handy cup size converter chart:
US-UK Cup Size Converter
|American Cup Size||UK Cup Size|
What You Need to Know About Bra Size Charts and Calculators
While bra size calculators and charts can give you a useful starting place for your bra sizing exploration, they can’t be wholly applicable to everyone all the time and in all brands.
To best use a bra size calculator or bra size chart, you’ll need to:
- Find a bra size calculator or bra size chart that’s reliable
- Take your underbust measurement
- Take your bust measurement
- Use the bra size calculator or bra size chart to find your starting place size.
- Experiment by trying on many different brands and styles in that size. If you’re having consistent issues, adjust accordingly.
It’s also possible to convert between the various bra sizing schemas of different countries using a bra size converter, with US-UK conversions among the most common.