What this calculator does
The usual guidance keeps the mirror narrower than the vanity, by 4 to 6 inches for a single and about 8 for a double. A 36 inch vanity therefore suits a mirror around 31 inches wide.
Narrower reads as deliberate; equal or wider reads as a mistake. The eye picks up the vanity edge as a reference line, and a mirror overhanging it looks like it was bought for a different room. The exception is a deliberately full-wall mirror, which reads as a design decision rather than a mis-sized object.
The formula
The mirror width is the vanity width less a setback, 5 inches for a single vanity and 8 for a double. The height is the space between the vanity top and the ceiling, less an allowance for the gap above the vanity and below the ceiling. The result is a recommendation, and a mirror within an inch or two of it will look right.
| Term | Meaning |
|---|---|
| Vanity | The basin unit below the mirror, whose width sets the reference. |
| Clearance above vanity | The vertical space available between the vanity top and the ceiling. |
| Double vanity | Two basins, usually taking either two mirrors or one wide one. |
| Sight line | Eye height at the mirror, which varies between users and should sit within the glass. |
The inputs explained
| Field | What to enter |
|---|---|
| Vanity width (in) | Vanity width in inches. |
| Vanity height (floor to top) (in) | Vanity height, floor to the top surface. Standard is around 32 inches. |
| Ceiling height (in) | Ceiling height. |
| Vanity type | Single or double vanity. A double takes a larger setback. |
When to use it
Buying a mirror for a new vanity
Mirrors come in stock sizes and the recommendation identifies which to look for.
Planning a bathroom renovation
Mirror and lighting positions are settled together, and both depend on the vanity.
Deciding one mirror or two
A double vanity can take a single wide mirror or a matched pair, and the width figure informs the choice.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
What mirror suits each vanity?
A range of vanity widths with the recommended mirror.
| Vanity width | Recommended mirror width | Recommended mirror height | Clearance above vanity |
|---|---|---|---|
| 24 in | 19.0 in | 52.0 in | 64.0 in |
| 36 in | 31.0 in | 52.0 in | 64.0 in |
| 48 in | 43.0 in | 52.0 in | 64.0 in |
| 60 in | 55.0 in | 52.0 in | 64.0 in |
Questions
Should the mirror be as wide as the vanity?
Narrower, usually by 4 to 6 inches on a single vanity. The vanity edge acts as a visual reference, and a mirror matching or exceeding it tends to look mis-sized. A deliberately full-wall mirror is a different design decision and reads fine.
How high should a bathroom mirror hang?
The centre roughly at eye level for the people using it, commonly with the bottom edge 5 to 10 inches above the vanity top. Households of differing heights are better served by a taller mirror than by compromising on the centre position.
One mirror or two over a double vanity?
Either works. Two mirrors, each centred on a basin, give each user their own and suit a symmetrical layout. One wide mirror makes the room feel larger and is easier to light evenly. The width figure here assumes a single mirror spanning the pair.
Does lighting affect the size?
Yes. Sconces flanking the mirror need wall space either side, which constrains the width more than the vanity does. Lighting above the mirror reduces the height available. Settle the lighting layout before finalising the mirror.
For ventilation in the same room, see the air changes per hour calculator. For tiling, see the grout calculator.