Too wide unbalances the wall; too high leaves shadows on your face. Here’s the number that decides it, plus double sinks, mounting height, and common mistakes.
How Wide Should the Fixture Be?
Choose a vanity light about 75% of the width of the mirror, and never wider than the mirror itself.
If there’s no mirror yet, size the fixture at about one-third of the vanity width instead.
Quick math for common setups:
- 24-inch vanity: an 18-inch light is a strong fit, though a 24-inch fixture can work if the mirror is wide enough.
- 36-inch vanity: 20- to 30-inch lights.
- 48-inch mirror: a 36- to 38-inch light bar.
Measure the mirror, not the vanity, whenever the two differ. The mirror sets the visual boundary.
One Sink or Two: Sizing a Double Vanity
For a double vanity, either run one longer fixture centered over the sink zone or split into two fixtures — one per mirror area — for even illumination with fewer shadows. Many 48-inch and wider vanities handle a single 36- to 48-inch bar or two smaller fixtures equally well.
With one large mirror over both sinks, measure the countertop width, divide it in half, then size each side as its own zone. Separate fixtures generally win on wider vanities: a single centered bar lights the center hard and the outer edges softly, showing up as shadowing when two people share the sink.
Our roundup of two light vanity light fixtures covers options sized for these paired setups.
Where to Mount It
Some above-mirror bars sit just 2 to 3 inches above the mirror, so check the fixture’s instructions before drilling.
Confirm the fixture suits a bathroom: many LED vanity bars are rated for damp locations rather than wet zones, so a light near a shower or tub needs a matching rating. Most are dimmer-compatible, but compatibility varies by fixture — check the spec sheet.
| Setup | Fixture Width | Mounting Height |
|---|---|---|
| Single mirror | ~75% of mirror width | 75-80 in. above floor |
| No mirror yet | ~1/3 of vanity width | 75-80 in. above floor |
| 24-in. vanity | 18 in. (24 in. possible) | 6-8 in. above mirror top |
| 36-in. vanity | 20-30 in. | 6-8 in. above mirror top |
| 48-in. mirror | 36-38 in. | 6-8 in. above mirror top |
| Double vanity, one mirror | Half-width per side | 75-80 in. above floor |
| Double vanity, split lights | Centered per sink zone | 60-66 in. for sconces |
| Side sconces | 18-24 in. from centerline | 60-66 in. above floor |
Mistakes That Undo a Good Fit
Most sizing errors trace back to measuring the wrong thing or hanging the light too high.
- Oversizing past the mirror edges — the light should frame the mirror, not swallow it.
- Mounting too high — face illumination drops and shadows take over.
- One centered bar on a large double vanity — separate zones reduce shadows when two people share the counter.
Measure the mirror width, multiply by 0.75, round to the nearest fixture size, then check mounting height against your finished floor before drilling. Two numbers, one tape measure, and the fixture lands right the first time.
FAQs
Should the light be wider than the mirror?
Keep the light at about 75% of the mirror’s width so the mirror edges stay visible.
How far above the mirror should a vanity light hang?
Check your fixture’s instructions, and keep overall height around 75 to 80 inches above the finished floor.
What size light works over a double vanity?
For a vanity 48 inches or wider, either one 36- to 48-inch bar or two smaller fixtures works. With a single large mirror, divide the countertop width in half and size each side as its own zone. Separate fixtures over each sink reduce shadows better than one centered bar.
References & Sources
- Home Depot. “Vanity Lighting Buying Guide” Supports the 75%-of-mirror sizing rule, the 4-inches-shorter than vanity guideline, and mounting height.
- Lowe’s. “How to Choose Vanity Light with Right Size” Supports the 75%-80% range for above-mirror fixtures and double-vanity sizing.
- Lowe’s. “Vanity Lighting Guide” Supports placement heights and side sconce positioning.
