Victoria's Secret and most contemporary bra makers employ a three-step method to size brassieres that works well with transgender women and crossdressing men: measuring band size, measuring bust size and calculating cup size. If a man wears breast forms, the process involves measuring band size and determining ideal cup size.
To measure band size, wrap a tape measure under your arms and ascertain chest circumference just above your breasts. The appropriate location is when the tape measure is in accordance to where the bra strap meets the bra. Round the number down to the closest even number if the result is an odd number.
To measure bust size, keep the tape measure horizontal with the ground, stand tall and measure around your chest to the fullest part of your breast. Round up to the nearest inch if the number is between inches. To ascertain your cup size, subtract the band size from the bust size and compare the difference with a cup size chart. For example, if the difference is 1/2-inch to 1-inch, the cup size is an A, whereas if the difference is 7 inches, it would be a G cup size.
If wearing breast forms, your cup size is based on how you want it to look. Typically, a man with a small frame chooses a B or C cup size, a man with a medium frame opts for a C or D cup, and a man with a large frame prefers a D cup or larger.