Find Your Real Bra Size
Use the slideshow to the left to find your
Five Measurements and enter them below.

1. Snug Underbust: inches
2. Tight Underbust: inches
3. Standing Bust: inches
4. Leaning Bust: inches
5. Lying Bust: inches
Estimated Bra Size
Nearest Sister Sizes
This calculator finds your UK bra size. If you would like to convert to another size, please see the charts below.

5/25/2014 05:00 AM EST Small corrections site wide. Calculator function now averages all three bust measurements instead of using the lying measurement only in certain circumstances.
5/1/2014 03:00 AM EST Version 3.0 goes live and is posted to r/abrathatfits. The page layout/design has been completely redone and many new pages are added to the site.
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

Older Versions

Version 1.0
Version 2.4