A very large fireplace can overpower a small rectangular mirror, so you may want to opt for a larger mirror with a more interesting shape. If the fireplace is centered on the wall, a round or oval mirror is ideal, as it will draw the eye to the fireplace and create the illusion of more space in the room.

Instead of choosing a small mirror according to the size of the fireplace, you can select larger mirrors so long as they do not exceed the width of the mantle. The average mirror height should be 4-5 inches below the cornice. Ensure that there are at least 3″ – 6″ gaps between the top of the mantle and the wide edge of the mirror.