Measuring straight out from the wall to the bottom of a long sleeve, clothing hangs 24 inches away from the back wall of a closet. Therefore, reach-in closets need to be a minimum of 24 inches deep after drywall.Remember that your plans are drawn based on frame before drywall installation.irst of all, as mentioned above, clothing hangs away from the back wall 24 inches. If a reach-in closet is 24 inches deep, any clothing hanging behind the return wall is completely hidden from view and difficult to access.