A few ways to understand how your clothes should fit.
The Blazer/Shirt Collar– Your blazer collar should never conceal or stand away from the back of your shirt collar. Place two stacked fingers between your neck and shirt collar, you should have a comfortable amount of space to be able to eat and converse without choking.
The Shirt Cuff– You should always display a quarter-inch of your shirt cuff. Anything more, your sleeves are too long and you should visit your tailor.
The Trouser Bottoms– Very little fabric should touch your shoes. Ask your tailor to shorten your trousers leaving around a one-inch break.
The Shoulder– The outline of your own shoulder shown not appear through the jacket (that means it is too small). Opposite of that–the sleeve’s head should never sag (that means your jacket is too big).
The Jacket Length – Stand with your hands to your side and make a fist. The standard rule is–the bottom of the jacket should be parallel with your knuckles. (Just make sure it is enough to cover your ass dude).