According to the fashion gurus at UMen magazine, these tips are the perfect way to properly measure a gentlemnan's suit.
Shirt: Measure your neck with tape measure to know your shirt size, a shirt should not be too loose or too tight around the neck. As for the length of sleeves, the cuffs should hit the bone at the top of your hand.
Trousers: Trousers are not supposed to fit like jeans, the length should hit the top of your shoe heel, it should not break too much. If the trouser has cuffs, they should be no less than 1.5 inches or 3.800 cm.
Jacket: The jacket should always be loose and comfortable, the sleeve should show ¼ to ½ of your shirt cuff under the jacket.
Socks: Dress socks should always cover the calves, they also have to match or be darker than the suit.
The Windsor: This is the gentleman’s knot, it looks good with every collar.
Adapted from: UMen