Bathroom Mirror Size Calculator

As a general rule, your bathroom mirror should be no wider than your vanity — and ideally 2 to 4 inches narrower on each side. For height, the mirror should fit comfortably in the wall space between the top of the vanity and the ceiling or light fixture, typically leaving 4–8 inches of clearance below and 8–12 inches above.

Start by measuring your vanity width and subtract 4–8 inches total (2–4 inches per side) to get your target mirror width. For height, subtract the vanity height plus desired clearances from the ceiling height. This gives you the maximum usable mirror height. Our calculator does all of this automatically once you enter your measurements.

For a double vanity, you have two options: one large mirror that spans the full vanity width (minus a few inches on each side), or two separate mirrors centered over each sink. If using one mirror, apply the same rule — keep it slightly narrower than the vanity. Two mirrors each typically equal the individual sink section width, with similar side clearances.

For a 36-inch vanity, a mirror between 28 and 34 inches wide is ideal. This keeps 1–4 inches of space on each side, which looks balanced and avoids a crowded appearance. If you prefer a bolder look, you can go up to the full 36 inches wide, but avoid going wider than the vanity itself.

For a 30-inch vanity, a round mirror with a diameter of 24–28 inches works well. Round mirrors are naturally more compact visually, so you have a little more flexibility. The mirror should still be noticeably narrower than the vanity to maintain proportion and not feel cramped.

The mirror should be narrower than the vanity — typically 70–90% of the vanity width. Height-wise, aim for a mirror that fills the available wall space naturally, using the formula: ceiling height minus vanity height minus clearances. Taller mirrors can make a bathroom feel larger and more open.

It's generally not recommended to use a mirror wider than your vanity, as it can look visually unbalanced and may conflict with nearby walls, towel bars, or fixtures. However, in some modern or frameless mirror designs, matching the exact vanity width is acceptable if done intentionally as a style choice.

Both dimensions matter, but width is typically the primary constraint since it must relate to vanity width. Height affects how functional the mirror is — a mirror that's too short may not reflect your full face comfortably when standing. Aim for a mirror at least 24–30 inches tall for practical use.