A couple of months ago I wrote about Playtex UK bra calculator and the math it did to suggest a (wrong) bra size, which is now removed from their site :) .

Now I'll take a look at their US sister site which also has a bra calculator, which also does the +5 thing. So here's how they do it.

Disclaimer: Bratabase.com does not endorse this method or its results.

The site will ask you for your bust and ribcage perimeter, both must be in inches as it will check that they contain that they are characters long.

The calculations are pretty simple then.

The band size

Playtex suggest to add 5"

  • If your ribcage is lesser or equal than 37", then your band size equals to your ribcage plus 5.
  • If your ribcage is greater than 37", then just add 3 to get your band size.
  • If the resulting band is an odd number, then use the immediate superior even number.

Only add 3" if your ribcage is greater than 38" Round up!!

The cup size

The cup calculation is pretty straight forward, just subtract your entered bust measurement minus the calculated band and look up your cup in this table:

Cup size table

Difference Cup
0 AA
1 A
2 B
3 C
4 D
5 DD
7 G
more than 7? Sorry, but your measurements are out of range, you freak! *

* The _you freak_ comment was added by me, as that is what I feel the message communicates. Playtex' message is "Sorry, but your measurements are out of range"


Error message

Even though the calculator can go up to G cups, I strongly think they should change the "your measurements are out of range"* message to a warmer "We are sorry we only stock bras up to G cup" and link the user in the right direction instead of making her feel it is her fault your calculator doesn't go higher. Your measurement's are not out of anybody's range.

Band size

Anyway, The biggest flaw here is the +5 calculation, with the funny +3 twist if your ribcage is bigger than 38". This leads to interesting situations as someone with a 39" back will be recommended a 42 band size, as someone with 36" back will also be recommended a 42 band bra!! Which is plain wrong if you ask me.

Of course, the +5 will lead to ridiculous suggestions alone, someone with a 30" back can not possibly be wearing a 36 band bra!

Cup size

When having your band size so far off, your cup size will be as skewed. In the case of a girl with a 30" back and a 38" bust, the site will recommend a bra size 36B!! which is is totally off. That girl is closer to the 30G realm than a B cup /facepaml

Even if you are going to do rounding, I would recommend rounding down instead of rounding up. You are always less likely to make a mistake of having a too small band bra than a too big bra which is the most common mistake .


Even if the calculator is intended to be used as a starting point only, the starting point is too far off to begin with.