The most basic thing is to measure the size of the front and rear armholes with a soft ruler (for example, the front armhole 14CM and the rear armhole 14.5CM, which is generally a little longer than the front, totaling 28.5CM).

Armhole height: 1/4(7.2cm) of the total armhole. The length of the vertical line in the middle is called the height of the sleeve hill.