Find your mirror size

A good rule of thumb is to keep the mirror a little narrower than the vanity — roughly 70–80% of the counter width — so it sits centered with a few inches of wall on each side rather than overhanging the edges.

You have two good options: one wide mirror that spans most of the counter, or two separate mirrors centered over each sink (each about the width of its basin). Both read as intentional — choose based on whether you want one continuous reflection or two defined stations.

Center the mirror at eye level for the people who use it most. In practice that usually puts the bottom edge a few inches above the backsplash and the mirror's center around 60–65 inches from the floor.

Generally a touch narrower, not wider. A mirror that matches or exceeds the countertop width can crowd wall sconces and look oversized; leaving a small margin on each side keeps the wall balanced.

Leave clearance for the fixtures — a mirror that fits comfortably between sconces looks balanced. If you'd rather skip separate sconces, a backlit or front-lit LED mirror provides the face lighting on its own.