A mirror that is too small looks lost and throws poor light back at your face. One that is too wide crowds the wall lights and splashback. The sizing rules below are simple, and once you know your vanity width, the rest follows from three measurements.
Width: Stay 2 to 4 Inches Narrower Than the Vanity
Make the mirror 2 to 4 inches narrower than the vanity unit below it, leaving 1 to 2 inches of breathing room on each side. For a 36 inch vanity, choose a 32 to 34 inch mirror. For a 48 inch vanity, choose 44 to 46 inches. For a 24 inch cloakroom vanity, a 20 to 22 inch mirror is right. Never go wider than the vanity. You can test combinations quickly with our Bathroom Mirror Size Calculator by entering your vanity width and sink layout before you shop.
Centre It Over the Sink, Not the Wall
Centre the mirror over the sink basin, which is not always the centre of the vanity or the room. On a 48 inch vanity with an offset basin, an offset mirror looks deliberate; a wall-centred mirror over an offset basin looks like a mistake. Mark the basin centreline on the wall with painter’s tape and work outwards from there. Most people are best served by a mirror whose vertical centre sits at about 57 to 60 inches from the finished floor.
Height and Mounting Position
A practical mirror height is 28 to 36 inches for a single vanity. Hang the bottom edge about 5 inches above the top of the faucet — not the splashback, the faucet — so you can clean behind it. Leave at least 6 inches between the top of the mirror and the ceiling or the bottom of a bulkhead.
Double Vanities: Two Mirrors or One Wide One?
Two separate mirrors, each 2 to 4 inches narrower than its sink zone, look tailored, cost less to replace if one breaks, and let you place a wall light or sconce between them. One wide mirror reflects more light, makes a small bathroom feel larger, and is cheaper to buy and hang. Choose the wide one if the room is short on natural light.
Lighting Clearance
Plan the lights before you fix the mirror width. Sconces mounted either side of the mirror need 3 to 4 inches of wall space between the mirror edge and the fitting. For an overhead bar light, keep its bottom edge at least 4 inches above the top of the mirror to avoid a hard reflected glare line at eye level.
Common Mistakes
Buying a mirror the full width of the vanity, hanging it so high that a shorter user only sees their forehead, and centring it on the wall instead of the basin. Measure vanity width, basin centre, and faucet height, in that order.