How big do these mirrors need to be?

If you need mirrors because two girls need the same bathroom at the same time, you also need more storage space because each girl needs space for her own cosmetics and stuff.

You might consider opting for a recessed medicine cabinet that has a mirror door.
That way, you get a mirror and additional storage space at the same time.



This cabinet will be 14 1/2 inches wide so that it fits between two wall studs. You attach it by screwing it to those studs with screws driven through holes in the side walls of the cabinet. You can also get recessed cabinets in a 22 1/2 inch width to fit 24 inch wall stud spacing.

If you opt for a surface mount medicine cabinet, you're not restricted to the stud spacing, and you can get a much larger mirrored cabinet they can both use:


In the above picture, it looks like the stuff inside the cabinet is reflecting off the back of the cabinet door as though the miiror is installed on the wrong side of the door. That's just to let you know that the front of the cabinet door is a mirror; not the back.

You can also get large surface mount medicine cabinets with multiple mirror doors so they don't fight over the door position.



Home Depot should have all kinds of 'em.