Calculator
Bathroom vanity lighting calculator
Tell us about your room and mirror to get a target brightness in lumens, a split between vanity and ceiling light, a color temperature range and where to put the sconces. It updates as you type and nothing leaves your device.
2,650 lumens target
Worked example (shown when scripts are off): a 40 square foot bathroom with a 30 inch mirror, medium walls and a window needs about 1,650 lumens at the vanity plus 1,000 for ambient light, so about 2,650 in all. In 800 lumen bulbs that is roughly 3 at the vanity and 2 overhead.
A starting point
Published lumen guidance varies between sources, so treat this as a range to aim for. A dimmer lets you tune the result.
How the calculator works
Lumens measure how much light a bulb gives off, and the number is printed on the box. The calculator adds two parts. The vanity part is about 55 lumens for each inch of mirror width, with a minimum of 1,600 and a maximum of 4,000. That follows manufacturer guides that cite the American Lighting Association, which suggest 1,600 to 3,000 lumens at a single-sink mirror and 3,000 to 4,000 for a double sink. For makeup or shaving it adds 25 percent.
The ambient part is 20 lumens per square foot, the low end of the 20 to 50 range attributed to the Illuminating Engineering Society. It is multiplied by 1 for light surfaces, 1.25 for medium and 1.5 for dark, and by 1.15 when there is no window. Those multipliers are our own assumptions, because dark tile and walls absorb light, and a windowless room has no help in the daytime. The optional accent light is a quarter of the ambient figure, and it is not counted in the total.
Worked example
A 5 ft by 8 ft bathroom is 40 square feet. A 30 inch mirror gives 1,650 lumens at the vanity. Medium walls and a window give 40 times 20 times 1.25, or 1,000 lumens of ambient light. That totals 2,650, or about 66 lumens per square foot. With 800 lumen bulbs as an example, that is three at the mirror and two overhead. Bulbs at 450 to 600 lumens each work too if you use more of them, and they glare less.
Color temperature and CRI
Warm white at 2700K to 3000K feels calm and suits general use. For makeup or shaving, 3000K to 4000K shows skin tone and stubble more truthfully. With no window, 3000K to 3500K keeps the room from feeling like a cave. Pick one range and use it everywhere, since mixed bulbs look patchy. Aim for a color rendering index (CRI) of 90 or higher at the mirror so skin tones read correctly.
Where to put the light
Light from both sides of the mirror cross-lights the face and removes shadows. Guides we checked put sconce centers at about 60 to 66 inches from the floor, roughly eye height. Spacing varies by source, from about 28 to 30 inches up to 36 to 40 inches, so choose by your mirror and face width, keeping each sconce a few inches from the mirror edge. If you prefer a single bar above the mirror, guides give about 75 to 80 inches from the floor, in a width of roughly three quarters of the mirror or a little more. A bar alone casts shadows under the brow and chin, so side light is better where you can do it.
Limits and safety
This is a planning aid, not a lighting design. Rooms with a very high ceiling, a lot of glossy dark tile or an unusual layout need more thought. The target is for evening use, because a window does not help after dark. Fixtures in the shower zone or near water need a damp or wet rating on the label. Turn off the breaker before changing any hardwired fixture, and hire a licensed electrician if you need new wiring, a new box or a new circuit. Local electrical code applies.
Where this comes from
We checked a lighting manufacturer's vanity buying guide (lumens by vanity type, 2500K to 3000K, CRI 90 or higher, sconce height and spacing, above-mirror heights, citing the American Lighting Association and IES guidance) and several retailer and lighting guides summarizing the American Lighting Association and Illuminating Engineering Society numbers. We did not read the original standards, so the lumens per square foot figures are secondary. Sources disagree on sconce spacing and total lumens per square foot, which is why the result is a range to aim for.