What is standard height for a mirror to be hung over a mantle?

There is no standard height for hanging a mirror over a mantel. It will depend upon the height of the mantel, the dimensions of the mirror, and the use for which the mirror is intended.

If the mirror is intended to be useful for people grooming themselves, it will need to be at a height where they can see at least their shoulders and up. A bottom edge no higher than 1.4m would cater for average adult heights. The height of the top edge should also be considered for this use. It should be a little over the head height of the intended users. A top edge 2m or above would cater for average adult heights.

If the mirror is intended to be an item of visual interest in itself, then it can be set at a height that suits the proportions of the mantel height, ceiling height and the size of the mirror. Often, allowing more space abover the mirrror than between the mirror and the mantel looks good. Every situation is different. Check this before hanging the mirror by making a quick paper cut-out the size of the mirror, and trying different positions.