A properly fitted tuxedo jacket lies smoothly from shoulder to shoulder across the back, with enough room for comfortable arm movement (have your groom-to-be give you a hug to gauge his comfort level). If the shoulder padding extends beyond his shoulders, the jacket is too big; if the jacket creases in the back, it's too small.
Formal dressing requires that the waist of a man's trousers never be exposed. If your guy opts to wear a vest, he should leave the bottom button undone (the portly King Edward VII started this trend at the beginning of the 20th century). If your groom chooses to wear a cummerbund instead, make sure the pleats face up.
If your fiancé is tall and slim, flat-front trousers are a great pick; they're cut slimmer through the legs and hug the hips nicely. Traditional pleated pants have a more relaxed fit, making them ideal for huskier body types. The pants' crease should cross the middle of his kneecap, and any pockets should lie flat against the leg—if they gape open, he needs a larger size.
The standard length for men's formalwear trousers is approximately one and three-quarter inches from the floor (with shoes on); the pant legs should break on the top of the shoe and angle slightly downward in back.
Hot Under the Collar
If your guy complains that dress shirts are uncomfortable, his shirt may simply fit poorly. Have him do the finger test: When his shirt is buttoned to the top, he should be able to slip his forefinger between the shirt's collar and his neck. If more than one finger fits, the shirt is too big; if his finger doesn't fit at all, it's too small.
Tying the Knot
Long ties are a popular choice in formalwear today; just make sure the tie is not so long that it peeks out from the bottom of your groom's vest. If he plans on wearing a bow tie, remind him that the wings of his shirt collar sit behind—not atop—the tie.
The perfect finishing touch to a tuxedo, a boutonniere should always be worn on the left lapel and tilt slightly outward. If he chooses to wear a pocket square instead, it should coordinate with his other accessories.
His jacket sleeves should fall at least below the crease of his wrist, but not reach past the fleshy part of his thumb. His shirt sleeves should extend one-quarter to one-half inches beyond the jacket sleeve.
Remind your groom to make sure he buttons his jacket while being fitted—first, to check that his lapels lie flat and, second, to be certain that the jacket is the correct size. If it's the right fit, it will taper slightly at the waist and then drape comfortably to the hip.
The proper length for a tuxedo jacket is one that covers a man's derriere and gives his legs the longest line possible. For a jacket that is perfectly suited to your groom's proportions, have his tailor measure him from the base of the back of his jacket collar straight down to the floor. Divide this measurement in half, and you have the best length for his physique.
The color of his formalwear trousers dictates the color of his footwear: Black patent leather shoes are worn with black pants, white shoes with white trousers and so forth. Remember that his socks ought to coordinate, too. Be sure he brings his shoes to his fitting to ensure the pant hem is the proper length.