Measuring the headboard. The optimum height for any headboard is no higher than the midpoint of the lowest wall in the room. This is so that the headboard does not draw all of the attention away from the depth of the room, thereby making it appear smaller. The goal is to make your room look as spacious and roomy as possible, so having a headboard that only reaches halfway up the wall will help keep your room looking more open. To truly appreciate the headboard that you choose, try to find a fabric that either matches most of the other furnishings of the room, or change the furnishing to match headboard. You may also want to consider purchasing some new bed shawls, duvets, pillow covers, and other bed accessories to further compliment your bed.
Also be sure to measure the bed frame, if you already have one. This will also need to fit within the headboard. The general rule when measuring the height of the headboard is this: measure half way up the wall of the room where the headboard will be placed against. Your headboard should never exceed this height! Try to find a headboard that either reaches half way or down to a few inches below that point. This will prevent the headboard from "crowding" and overpowering the room.