I calculated that my next parents' body mass index is 26, which deviates from 18.5-23.9, and some of them are overweight. Now I will tell my parents the standard size of men's shirts, hoping to help you:

1S 165/ 105

2M 170/ 1 10

3L 175/ 1 15

4XL 180/ 120

If the parent is online shopping, in view of the fact that the size of the webpage is the size of the tile of the clothes, and the human body is three-dimensional, it is necessary to vacate 3-5CM of space. Cotton-padded jacket clothes don't need to be too thin. In view of many years' experience in buying clothes, it is safe to buy XL.