How It Works

This calculator follows the sizing guide made by . It uses JavaScript functions to calculate the measurements that you provide and return to you an estimated bra size in both UK and US sizes as well as the nearest sister sizes.

Due to recent theft of this calculator, I have taken down the step by step process of the JavaScript function it uses. If you would like to know more about how your size was calculated, you can contact /u/irisflame on Reddit or post a size check in /r/abrathatfits.

Differences from the Original Guide

This calculator is not perfect and is meant to be used only as an estimation for your size. After working out a few kinks, there are now very few differences between this calculator and the guide. Below are the current differences that still exist.

• This calculator cannot take your breast shape into account, yet.
  • It does, however, consider the difference between bust (lying) and bust (leaning), which is usually a high number in projected or pendulous breasts

Update Log

3/24/2014 01:30 PM EST Removed the US bra size because it was confusing many people. Added a UK to US converstion chart under the "How to Use" section.
3/20/2014 04:45 PM EST Changed hosts and URLs. We are now our own website! Also, cleaned up and organized the code in the process.
3/20/2014 02:30 AM EST Changed the method of choosing bust size so that if the difference between standing and leaning is greater than 2, it finds the average (instead of being greater than or equal to 2). Now gives you two cup sizes if the difference between your underbust and bust falls between two numbers.
3/19/2014 02:00 AM EST Fixed the method of sister sizing down for significant "squish."
3/18/2014 01:00 AM EST - Added underbust (tight) and bust (lying) measurements and integrated them into the calculation function as suggested in the original thread on Reddit. Changed the layout slightly. Updated the About section. Changed to Version 2. Posted to r/abrathatfits.
3/17/2014 08:30 PM EST - Changed "How to Measure" section to "How to Use." Added subsections "What Your Results Mean" and "What Are Sister Sizes?" Added a sister size chart for reference. Added "Update Log" and "Future Plans" to the "About" section.
3/17/2014 05:50 PM EST - Added KK to the UK Cup size list, as it was mistakenly left out.
3/17/2014 04:30 AM EST - Changed the function that automatically sizes up band sizes of 32 or below so that it now prompts you to consider sister sizing up for comfort. Changed the function that automatically sizes down band sizes of more than 36 so that it now prompts you to consider sizing down for support.
3/17/2014 03:45 AM EST - Bra Size Calculator goes live and is shared on r/abrathatfits.

Future Plans

Here are some things that will be incorporated into the calculator later on.

• Use of breast shape
• Guides for how breast shape and other factors affect your bra size
• Suggested bra brands for your size and shape
• Other EUR bra sizes
• Update the layout and design of the page so that is super awesome and looks like an expert made it, and not bland like a 12 year old made it.

Credits

This calculator was coded by T. Linton () with the help and guidance of Joe Saltsman ().

JavaScript must be enabled on your browser for this calculator to work.

underbust (snug): inches
underbust (tight): inches
bust (standing): inches
bust (leaning): inches
bust (lying): inches

	Estimated Bra Size	Nearest Sister Sizes
UK	N/A	N/A	N/A
/r/ABraThatFits uses UK bra sizes, and we recommend that you do as well. If you would like to convert your size because you are looking at buying a US brand bra, please see "What Your Results Mean" in the "How to Use" section to your right. All sizes given are merely estimates and should not be considered definite. Certain breast shapes and size ranges may require slightly different methods of calculating bra size; if you would like a more personalized calculation, consider posting a Measurement Check post on . In addition, there can be slight variations between brands or even colors. You may need to try on a variety of bras surrounding this estimated size before you find one that fits you perfectly. Do not get discouraged! Once you find that perfect size, your body will thank you! :] Enjoy!

Before You Begin

You should not be wearing a bra when you take these measurements. You should also not distort your breasts in any way while you are taking these measurements. Let them fall naturally.

The calculator takes measurements in inches. It will accept decimals as well, but not fractions.

Fraction 1/16 1/8 3/16 1/4 5/16 3/8 7/16 1/2 9/16 5/8 11/16 3/4 13/16 7/8 15/16

Decimal .0625 .125 .1875 .25 .3125 .375 .4375 .5 .5625 .625 .6875 .75 .8125 .875 .9375

What You Need

1. A soft/flexible measuring tape
   • If you do not have a soft measuring tape, you can use a piece of string and a ruler/yardstick instead.
2. Something to record your measurements with or on.
   • You will enter all of these into the calculator.

Definitions

Underbust - this is the line immediately below where your breast tissue attaches to your chest (called the inframammary fold)
Bust - this is the line across your breasts at their fullest point (usually at or near the nipple)

Measurements

1. Underbust (Snug): Measure your underbust with the tape "comfortably snug" (not too tight but not loose). Keep the tape parallel to the ground.
2. Underbust (Tight): Measure your underbust with the tape as tight as possible without breaking the tape (exhale for this measurement). Keep the tape parallel to the ground.
3. Bust (Standing): Measure your bust at its fullest point while standing. Keep the tape parallel to the ground.
4. Bust (Leaning): Measure your bust while leaning over at a 90 degree angle so that you are looking at the ground. Keep the tape perpendicular to the ground.
5. Bust (Lying): Measure your bust while lying on your back. Do not manipulate your breasts. Keep the tape perpendicular to the ground.

What Your Results Mean

The calculator is not perfect, but it is fairly accurate. The first bra size it gives you is your estimated bra size. The other two sizes are the nearest sister sizes for your estimated bra size.

If you have a 32 inch or less underbust, you might want to consider sister sizing up for comfort. If your breasts are rather large (GG+) you might need to keep the band size lower for added support. If you have more than a 36 inch underbust, you will also want to consider sister sizing down for support, since the band sizes greater than 36 tend to be stretchier.

You may need to try on surrounding band and cup sizes in order to find the perfect fit. Remember, not all bras are made with the same cut, so a 34G in one brand might not fit the same as a 34G of another brand. Breast shape also plays a role in determining your bra size. More on shapes will be added at a later time.

If you are looking to buy a US brand bra in your size, here is a conversion chart for cup sizes. Please note that US brands tend to be less consistent than UK brands, and you may have difficulty finding US brands with cups larger than a DDD.

UK	US
AA A B C D DD E F FF G GG H HH J JJ K KK L LL	AA A B C D DD/E DDD/F G H I J K L M -- -- -- -- --

What are Sister Sizes?

Cup size is entirely dependent on band size. Sister sizes hold the same volume of cup (amount of boob, if you will), but may fit better or worse depending on your preferred band measurement. For every band size you go up, you should go down an equal number of cup sizes, and vice versa.

For the purposes of this guide/calculator, the term "sister size up" means to go up in band size and down in cup size (32G > 34FF) and the term "sister size down" means to go down in band size and up in cup size (32G > 30GG).

Below is a chart with several sister sizes. Each row is a family - all the sizes listed on that row (same color) are sister sizes and have the same cup volume. Note that the further away you go from your estimated bra size, the less likely it is that the bra will fit. This chart is written with the UK sizing method, since it is more consistent.

26	28	30	32	34	36	38	40	42	44	46
26AA
26A	28AA
26B	28A	30AA
26C	28B	30A	32AA
26D	28C	30B	32A	34AA
26DD	28D	30C	32B	34A	36AA
26E	28DD	30D	32C	34B	36A	38AA
26F	28E	30DD	32D	34C	36B	38A	40AA
26FF	28F	30E	32DD	34D	36C	38B	40A	42AA
26G	28FF	30F	32E	34DD	36D	38C	40B	42A	44AA
26GG	28G	30FF	32F	34E	36DD	38D	40C	42B	44A	46AA
26H	28GG	30G	32FF	34F	36E	38DD	40D	42C	44B	46A
26HH	38H	30GG	32G	34FF	36F	38E	40DD	42D	44C	46B
26J	28HH	30H	32GG	34G	36FF	38F	40E	42DD	44D	46C
26JJ	28J	30HH	32H	34GG	36G	38FF	40F	42E	44DD	46D
26K	28JJ	30J	32HH	34H	36GG	38G	40FF	42F	44E	46DD
26KK	28K	30JJ	32J	34HH	36H	38GG	40G	42FF	44F	46E
	28KK	30K	32JJ	34J	36HH	38H	40GG	42G	44FF	46F
		30KK	32K	34JJ	36J	38HH	40H	42GG	44G	46FF
			32KK	34K	36JJ	38J	40HH	42H	44GG	44G
				34KK	36K	38JJ	40J	42HH	44H	46GG
					36KK	38K	40JJ	42J	44HH	46H
						38KK	40K	42JJ	44J	46HH
							40KK	42K	44JJ	46J
								42KK	44K	46JJ
									44KK	46K
										46KK