Calculate exactly how many lumens you need to light any room. Enter your room width, room length, ceiling height, room type, wall color, and light placement — and get back the total lumens required, recommended foot-candles, and room area so you can shop for the right bulbs or fixtures with confidence.
Total Lumens Required
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Room Area
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Recommended Foot-Candles
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Lumens per Sq Ft
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Suggested 800 lm Bulbs
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A general rule of thumb is 20–30 lumens per square foot for most living areas. Task-heavy spaces like kitchens and offices typically need 30–50 lumens per square foot, while relaxed areas like bedrooms can get by with 10–20 lumens per square foot.
Watts measure how much energy a bulb consumes, while lumens measure how much visible light it produces. A higher lumen count means a brighter bulb. Modern LED bulbs produce around 80–100 lumens per watt, so a 10W LED can deliver 800–1000 lumens.
A foot-candle (fc) is the amount of light that falls on a surface one foot away from a single candle. One foot-candle equals approximately 10.76 lux. To find total lumens needed, multiply the room's square footage by the required foot-candles for that space.
Dark walls absorb significantly more light than light-colored walls, meaning less light is reflected back into the room. A room with dark walls may need 15–25% more lumens than the same room with white or cream walls to achieve the same perceived brightness.
Higher ceilings mean light fixtures are farther from the surfaces you want illuminated. Light intensity diminishes with distance (following the inverse-square law), so rooms with ceilings above 9 feet generally require more lumens to maintain the same foot-candle level at floor level.
Kitchens typically require 30–50 foot-candles, translating to roughly 3,000–5,000 lumens for an average-sized kitchen (100–150 sq ft). Task areas like countertops and islands may benefit from additional under-cabinet or pendant lighting on top of general overhead lighting.
The lumen method estimates total lumens needed by multiplying room area (sq ft) by the required foot-candles for the room type, then applying a correction factor for ceiling height, wall reflectance, and light placement. This gives a reliable starting point when choosing bulbs or fixtures.
Divide the total lumens required by the lumens output of your chosen bulb. For example, if your room needs 3,200 lumens and you're using standard 800-lumen LED bulbs, you'd need at least 4 bulbs. Distributing fixtures evenly across the ceiling improves coverage and reduces shadows.