The position of your breasts should be at the middle of your shoulders and elbows.
It will calculate bra sizes for you.
Like the band, you should be able to slip a finger underneath the straps, but no more than two.
Order multiple sizes to find what works best.
This is critical because if the tape measure isnt straight you will get an incorrect measurement.
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.