When I first got employed,My Hr employer sent me the following email coat suits tricks
1.The shoulder into wall trick
Put on the suit with the outside of your shoulder facing a wall,slowly leanonto the wall.If the shoulder pad strikes first then scrunches before your shoulder gets there;Then the suit is to big for you

The shoulder and the pad should strike the wall at almost the same time

2.The hug test

Pretend your are going to hug someone,if it feels you are going to burst a seam, then its a small size.

3.Curled fingers
Let your arms hang relaxed at your sides,curl your fingers as if you are about to grab the handles of a wheelbarrow.Your coat tail should come to rest in the crevice your fingers have made.If its bunched up, it is toolong;if its dangling,its too short.
5.Armhole/handshake

Pretend you like you are about to shake someone hands,if the coat raises up with its strings being pulled then its too tight