A vanity light should measure about 75% of the mirror width and never extend past the mirror edges.
A fixture that runs wider than the glass above it throws the whole wall off balance, and one that runs short leaves the sink in shadow. The sizing math takes about a minute once you know which surface to measure — the mirror, not the cabinet.
How Do You Size a Vanity Light to the Mirror?
Measure the mirror width, multiply by 0.75, and buy a fixture close to that number without letting it project past the mirror’s left and right edges. Canarm USA’s sizing guide sets the target at roughly three-quarters of mirror width, and Home Depot’s vanity lighting buying guide lands in the same place with a retailer shortcut: choose a fixture about 4 inches narrower than the vanity overall, which works out to 2 inches of breathing room on each side.
Sizing to the mirror rather than the cabinet matters more than people expect. A 48-inch vanity with a 30-inch mirror needs a small fixture, even though the countertop is wide. Skip this step and a light bought to match the cabinet will overhang the glass on both sides.
Common targets from published guides:
- 24-inch vanity: about 18 inches
- 30-inch vanity: 22–28 inches
- 36-inch vanity: 26–28 inches
- 48-inch vanity: about 36 inches
What Changes on a Double Vanity?
Double vanities come down to one decision: one long mirror or two separate ones. A 60-inch or 72-inch setup works with a single wide mirror carrying one longer bar light, or two individual mirrors each getting its own fixture centered over a sink. Canarm’s guide recommends exactly those two approaches, and picking between them is mostly a matter of how the room is laid out — a shared mirror reads as one continuous space, while two mirrors split the counter into his-and-hers zones.
With a single wide mirror, apply the 75% rule to the full mirror width. With two mirrors, apply it to each one separately and hang a matching fixture over each sink.
If you are still comparing fixture types, this roundup of tested bathroom LED vanity lights covers bar lights and sconces side by side, which helps before you commit to a width.
Where Should the Light Sit on the Wall?
An overhead bar mounts with its bottom 6–8 inches above the top edge of the mirror, per designer guidance, so it clears the glass and throws light down onto faces. Side sconces are a different animal and sit at eye level, commonly centered around 60–65 inches above the finished floor.
The placement rule most people miss: a sconce above a mirror is the wrong fixture in the wrong spot. Sconces are made to flank the mirror on the side walls, while bars mount overhead.
| Vanity Width | Fixture Target | Best Layout |
|---|---|---|
| 24 in | ~18 in | One bar over a small mirror |
| 30 in | 22–28 in | One bar, centered on mirror |
| 36 in | 26–28 in | One bar or two flanking sconces |
| 48 in | ~36 in | One bar over a wide mirror |
| 60 in | 75% of mirror width | Two mirrors, one fixture each |
| 72 in | 75% of mirror width | Single long bar or twin fixtures |
| Any size, sconces | Eye-level, 60–65 in | Flank the mirror, not above it |
Do You Have the Right Fixture for the Job?
Before buying, check three things: the fixture width against your 75% target, the mounting height against the mirror top, and whether your layout calls for a bar or sconces at all. Home Depot’s buying guide notes that the mirror, not the cabinet, is the reference point, and that fixture style should follow the room’s existing finish.
One reminder on editions and layouts: vanity lighting terms and recommended clearances can shift between product lines and retailer guides, so confirm the current spec sheet for the exact fixture before ordering. Kichler’s published fixture specs are a useful reference for matching listed dimensions to your measured target.
When you have the width, the height, and the layout locked, the purchase decision is simple.
FAQs
Can a vanity light be wider than the mirror?
No — a fixture wider than the mirror looks unbalanced and casts light past the usable reflection area. Stay inside the mirror’s left and right edges, targeting about 75% of its width. If the fixture you love runs long, drop to the next smaller size rather than letting it overhang the glass.
What size light fits a 36-inch vanity?
Most guides put the target between 26 and 28 inches for a 36-inch vanity with a matching mirror. That keeps the fixture under the mirror edges while still spreading light across the whole counter. Measure your actual mirror first — a narrower mirror may call for something closer to 24 inches.
Should a double vanity have one light or two?
Either works. Two separate mirrors each get their own fixture centered over a sink, which lets each person control brightness. A single wide mirror takes one longer bar sized to the full mirror width. Pick based on whether you want the counter to read as one shared space or two zones.
References & Sources
- Home Depot. “Vanity Lighting Buying Guide” Sets the 4-inches-narrower sizing shortcut and mirror-based reference point.
- Canarm USA. “How to Determine Bathroom Vanity Light Sizes” Source of the 75% mirror-width rule, size examples, and double-vanity layouts.
- Ferguson Home. “Kichler 45569” Manufacturer fixture specs for matching listed dimensions to your measured target.
