Coat closets can get cramped, and it's because they're often designed with the same dimensions as any clothes closet. If you put specific guidelines in place for coats, the closet should never cramp your style.
Coats and Codes
The majority of building codes don't cover closets. The dimensions of any closet are decided by the builder, designer or owner. If you're in a position to choose the size of a closet intended to hold coats, you typically won't regret leaning toward the bigger sizes.
Closet width guidelines are subjective. The common coat closet is typically designed according to how much room is available, or how much room you're willing to give up. The general rule of thumb is to allow about 4 inches of width for an individual coat, or 48 inches of width for each person who uses the closet.
Most clothes closets have a depth of 24 inches, and many builders use the same depth for coat closets -- but that's typically not enough. Coats are wider than shirts, and get cramped at 24 inches. Coat hangers are typically 19 inches wide -- add a heavy coat and it's cramped at 24 inches. Coat closets should have a minimum of 28 inches of depth -- 30 inches is ideal -- to prevent sleeves and bulky coats from interfering with the closet door.
Coat closets typically employ the same doors as the existing interior doors in your home. Standard doors require 80-inch-tall openings, and that's fine for coats. Any variation in opening height looks odd or out of proportion to the other doors. The actual height on the inside of the closet is usually the same as the ceiling in the home, typically between 87 and 96 inches.
The door opening size is regulated by the return walls, which should be no wider than about 18 inches. The return walls are the face of the closet on both sides of the door. Anything wider than 18 inches closes off the sides of the closet, and makes it hard to reach coats that are tucked behind them.
The average coat closet might have a 2 foot, 8 inch -- called "two-eight" -- door, which is 32 inches wide. Standard doors can be more narrow, down to 24 inches, or wider, up to 36 inches, with individual sizes typically graduating in 2-inch increments.
Rough Door Openings
Rough door openings consist of the stud frame around the opening. The closet's rough opening size is calculated by adding 2 inches to the width of the door, and 2 1/2 inches to the height. For example, the average rough door opening for a 32-inch door would measure 34 inches wide, and 82 inches tall.
Coats typically require 46 to 66 inches of vertical space. If you plan on using only one rod, install it 72 inches from the floor. But if you plan on using two rods, it's common to squeeze the requirement, and install the higher rod at 80 to 84 inches, and the lower rod between 40 and 42 inches. The rod should be centered according to width, 14 or 15 inches from the back wall.