Hi Thanks for your question. The sconces are about 3'6" apart (on center). Or depending on the width of your mirror - try 6" from the side of the mirror. I specify the location as on center. Meaning on center of the light fixture. So take into consideration the back plate of the light fixture and adjust accordingly.

These were about 5'8" off the floor. But I adjust the height location based on where the bulb sits in the fixture. Sometime the bulb is higher than the wiring - sometimes it is lower. It's always best to have the fixture selected and in hand when trying to mark a sconce location. If not, the standard height of 68" -72" is a safe height range.

You can estimate the electrical location by taking the width of the sink or vanity and adding about 6" - 10" on either side. Or you can always just pull the electrical cable through the sheet rock and then cut in the electrical box once you've selected the fixture. If you aren't selecting the fixture for a while, then just run the electrical wire in the call to about eye level. Keep it centered on the sink but keep it within the wall. Once you have the mirror and fixtures selected, you can make a small opening in the wall and relocate the wiring. Just remember to leave enough wire length in the wall for the relocation.

Hope this helps!

one more question please what is the mirror width?

The mirror in that Powder Room was 2'6" wide