Calculate a perfect fit.

Measurement should be taken while wearing an unpadded comfortably fitted bra.

Band size
Measure around chest just under the arms and above the breasts. Be sure to keep the tape measure high on your back and level all the way around. Hold it snug but not tight.
Cup size
Measure around the fullest part of the bustline. Be sure to keep the tape measure level. Hold it snug ut not tight.

Straps

Bra straps should not slip or leave ridges on your shoulders. Try adjusting them for a better, more-comfortable fit.

Cups

If the bra cups gap, pucker or are not filled out, a smaller cup size is needed. If your breasts overflow at the top, push out on the sides or towards the center, try a larger size or different style.

Center seam

The center seam or gore should lie flat against your sternum. It should not cover or lie on top of any part of your breast. If there is a large gap, you may need to go up a cup size.

Underwire

If you've chosen an underwire bra, be sure that the wires are resting underneath your breasts on your ribs and not on your breasts themselves. If the wires are pressing against your breast tissue, you should consider a larger cup size or a wire-free style.

Bra band

The bra band should feel secure, but not tight. The lower edge of the band should be located below the shoulder blades. If it rides up, the strap may be too tight, the cups may be too small or the band size may be too large. If the band is too tight, you may need to go up a band size. The closure should fit best when it is fastened in the middle position. This gives you the ability to tighten or loosen the band in the future, as needed, for comfort.