I calculated that my next wife's body mass index is 20.4, which is between 18.5-23.9, which is quite standard. Now I'll tell you the standard size of a lady's blouse, hoping it will help you:

1S 160/84

2M 165/88

3L 170/92

4XL 175/96

If parents buy online, because the size on the web page is the plane size of clothes, and the human body is three-dimensional, it is necessary to vacate 3-5CM space. There is no need to wrap the coat like zongzi, so I personally suggest buying size M.