How many lumens for a 200 ft² living room?

For 200 ft² ≈ 18.6 m² at the recommended 200-lux residential level, you need 18.6 × 200 = ~3,700 lumens — about 4-5 modern LED bulbs (each ~800 lm) or one bright ceiling fixture.

What about color temperature?

CCT (correlated color temperature, in Kelvin) is independent of lumens/lux. 2700K = warm white (incandescent feel), 4000K = neutral, 6500K = daylight. Pick based on application, not brightness.

Why is direct sunlight 100,000 lux?

The sun emits ~3.85×10²⁶ lumens, at distance 1 AU the inverse-square law gives ~127,000 lux at the top of atmosphere; atmospheric attenuation drops this to 100,000 lx at noon clear sky.

CIE (Commission Internationale de l'Éclairage) S 017/E:2020 — Vocabulary of light and radiation. EN 12464-1:2021 — Light and lighting of indoor workplaces. IESNA Lighting Handbook 11th ed (2020). CIBSE Code for Lighting.

How many lumens for a 200 ft² living room?

For 200 ft² ≈ 18.6 m² at the recommended 200-lux residential level, you need 18.6 × 200 = ~3,700 lumens — about 4-5 modern LED bulbs (each ~800 lm) or one bright ceiling fixture.

What about color temperature?

CCT (correlated color temperature, in Kelvin) is independent of lumens/lux. 2700K = warm white (incandescent feel), 4000K = neutral, 6500K = daylight. Pick based on application, not brightness.

Why is direct sunlight 100,000 lux?

The sun emits ~3.85×10²⁶ lumens, at distance 1 AU the inverse-square law gives ~127,000 lux at the top of atmosphere; atmospheric attenuation drops this to 100,000 lx at noon clear sky.

CIE (Commission Internationale de l'Éclairage) S 017/E:2020 — Vocabulary of light and radiation. EN 12464-1:2021 — Light and lighting of indoor workplaces. IESNA Lighting Handbook 11th ed (2020). CIBSE Code for Lighting.

Lumens to Lux Calculator (lighting design)

Illuminance (lux) = luminous flux (lm) ÷ area. Inverse-square law for point sources at distance.

Result

Illuminance

80.00 lux

Corridor / parking lot lighting. (800 lm over 10 m²)

ModeArea-distributed (lm/m²)
Luminous flux800.0 lumens
Area10.00 m² (107.6 ft²)
Illuminance (lux)80.0000 lx
In foot-candles (US)7.432 fc
Activity-appropriate bandCorridor / parking lot lighting.
Bulbs of this lm needed for 500-lux reading level7
— Recommended target lux (EN 12464-1 / IESNA) —
Public areas (corridors)50-100 lux
Simple visual tasks (residential rooms)100-200 lux
Reading / writing (home + office)300-500 lux
Drafting / detailed assembly500-1000 lux
Fine inspection / surgery1000-5000 lux
Direct sunlight (outdoor reference)10,000-100,000 lux

Step-by-step

Lux = lumens / area = 800 / 10 = 80.00 lx.

How to use this calculator

Pick the geometry: "area" for spread illumination (room, parking lot); "point" for a directional source (flashlight, headlight, spotlight).
Area mode: enter total lumens of all bulbs in the room + floor area in m². Result is the average illuminance.
Point mode: enter the source's candela rating (from manufacturer specs) + distance in m. Inverse-square law applies.
Compare to the recommended-target table to size the right number of bulbs for the activity.

About this calculator

Lumens (lm) measure the TOTAL light output of a source — a bulb that emits 800 lumens does so regardless of how far away you stand. Lux (lx = lm/m²) measures how much of that light actually lands on a surface — depends on the area illuminated and the geometry. For diffuse area lighting (room with multiple bulbs covering the ceiling), illuminance = total lumens ÷ floor area. For a point source at distance, illuminance follows the inverse-square law: lux = candela / r², where candela is the source's directional luminous intensity. Lighting-design standards (EN 12464-1 in Europe, IESNA in US) prescribe target lux levels by activity: 300-500 lx for general office work; 1000+ for fine assembly; 50-100 for corridors. The conversion to foot-candles (US legacy): 1 fc = 10.764 lx.

Frequently asked

Because lux depends on how you use the bulb. The bulb emits the same total light (lumens) regardless of where you point it; lux is the lighting designer's job to figure out from room geometry.