The length of your jacket will determine how balanced your body appears.
Currently, men's suits are going through a transformation. For many years the style was that suits were worn at or below the buttocks. Today, with the slimmer fit, jackets are getting shorter and can be worn level with the jacket sleeve or slightly shorter. This only suits the slimmer male. The more classic your style of suiting the more traditionally dressed you will appear.
A tailor can shorten your jacket up to an inch/ 2 cm without messing up its proportions. It can be lengthened to the full extent of the hem allowance by introducing a fake hem. this can be tricky as well. Overall, you generally want this part to already be perfect when you’re buying a suit, even off the rack.