We have 3 lights across one wall, about 40 inches apart. Centered between them are 2 large rectangular mirrors (we have 2 sinks). I worked out how much space I had between sinks, what type & size of mirrors I wanted, then placed the lights so that they would have enough clearance from the side walls. The center of the light fixtures are about 6 1/2 inches from the edge of the mirror. Looks good to me. If you know the size of your mirror/medicine cabinet, make a paper cutout and tape it to your wall centered over your sink. Then decide exactly where you want your light fixtures. ps... I'm no pro, but this worked for me! pss... I bought lights from Restoration Hardware that are height adjustable, plus you can easily change them from up lights to down lights. It's called the Bistro sconce and is on sale now, I believe. I agonized over all of this... lighting is so difficult.

Hi, I would suggest having the top of the sconces just above eye level. This will create a nice illumination on those high walls. Here is a link that might be useful: Lake Lighting

Thank you. I wish I had posted earlier. I already have a light in the center of the dining room and need better lighting where the table is located and thus the sconces. The drapes are newly installed so I can't get rid of those at the moment....maybe in a few years.

I have three 11" Blade LED Wall Sconces two of which are between windows in a room with 8' ceilings. Bottoms of sconces are 65" from the floor and centers of the 4" electrical boxes to which the sconces are attached are 67" from the floor. Lowering the electrical boxes by 4" (to 63") would have made them too low, I believe.