What kind of standard is appropriate? Mainly look at the following points.
The first point is the collar. When you put on your shirt and button all the buttons, there should be a gap of one or two fingers between your collar and neck.
The second point is the shoulder. The shoulder seam should be at the edge of the shoulder. If the seam slides to the side of the arm, the shirt is too big.
The third point is the armhole, close to your armpit, but low enough so that he can't move when you move your arm. The smaller the armhole, the thinner the sleeve, and the more obvious the feeling of self-cultivation.
The fourth point is a long-sleeved shirt, which fits well. The sleeve length should be just at the base of your wrist or palm.
The fifth point is the body. The back of the shirt is sewn with pleats to make the waist closer to the body. A skilled tailor can slim the shirt by adding pleats.