Lux to Lumens Calculator
Convert between lux and lumens for any area. Includes a room lighting guide with recommended lux levels, energy cost estimator, and fixture count calculator.
Luminous Flux (lumens)
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Lumens (area in ft²) —
Extended More scenarios, charts & detailed breakdown ▾
Lumens
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Professional Full parameters & maximum detail ▾
Lighting Requirements
Required Lumens —
Energy & Cost
Total Wattage —
Annual Energy Use —
Annual Energy Cost —
How to Use This Calculator
- Enter the Illuminance in lux and the Area in m².
- Total lumens required appears instantly.
- Use Lumens to Lux tab for the reverse conversion.
- Use the Lighting Guide tab for recommended lux by room type.
- The Professional tab calculates annual energy cost.
Formula
Lumens = Lux × Area (m²)
To convert area: 1 m² = 10.764 ft²
Example
Kitchen 300 lux, 15 m²: Required = 300 × 15 = 4500 lumens. Use three 1500 lm bulbs.
Frequently Asked Questions
- Lumens (lm) measure the total amount of visible light emitted by a source in all directions — it describes the light source itself. Lux (lx) measures illuminance — the luminous flux received per unit area, equal to 1 lumen per square meter. The same 800-lumen bulb in a small bathroom (4 m²) produces 800/4 = 200 lux, while in a large living room (40 m²) it produces only 800/40 = 20 lux. Think of lumens as the total light available and lux as how bright the light appears on a surface. Other related units: candela (cd) measures luminous intensity in a specific direction; nits (cd/m²) measure the luminance of a display surface. A typical 60W incandescent bulb produces about 800 lumens; an LED equivalent uses only 8–10W to produce the same lumens.
- Lumens = Lux × Area (m²). If you know the required illuminance (lux) and the room area, this formula gives the total lumens needed from all light fixtures combined. Example: an office needing 500 lux with a floor area of 30 m² requires 500 × 30 = 15,000 lumens total. If using 1,500-lumen LED bulbs, you would need 15,000 / 1,500 = 10 bulbs. For the reverse, lux = lumens / area (m²). This assumes uniform illumination (perfect mixing coefficient = 1). In practice, a room utilization factor of 0.5–0.8 is used to account for walls, ceiling reflectance, and fixture efficiency, meaning you may need to divide the calculated lumens by 0.6–0.7 to get the actual installed lumens required.
- Recommended lux levels vary by task and space type. Standard guidelines (from CIBSE, IESNA, ISO 8995): office general work area = 300–500 lux; computer workstations = 300–500 lux; reception areas = 200–300 lux; corridors and hallways = 100–200 lux; conference rooms = 300–500 lux; classrooms = 300–500 lux; hospital wards = 100–300 lux; surgical suites = 10,000–100,000 lux; residential bedrooms = 100–200 lux; living rooms = 150–300 lux; kitchens = 300–500 lux; bathrooms = 200–300 lux; garages = 100–200 lux; outdoor parking = 20–50 lux. Sunlight on a clear day = 100,000 lux; overcast sky = 1,000–10,000 lux; full moon = 0.1 lux; candlelight = 10–15 lux.
- Required lumens = Required lux × Room area (m²) ÷ Utilization factor. The utilization factor accounts for light lost to walls, ceiling, and fixture efficiency — typically 0.5–0.75 for most rooms. Example: a 20 m² living room at 200 lux with 0.6 utilization factor needs (200 × 20) / 0.6 = 6,667 lumens installed. A simpler rule of thumb: multiply room area in m² by 25–50 lumens/m² for general home lighting (lower for ambient, higher for task areas). Common room sizes and rough lumen needs: 10 m² bedroom: 2,000–3,000 lm; 15 m² kitchen: 3,000–5,000 lm; 20 m² living room: 4,000–7,000 lm; 3 m² bathroom: 1,500–2,500 lm. Distribute across multiple fixtures for even coverage.
- 1 footcandle (fc) = 10.7639 lux. Footcandles are used primarily in the US; lux is the international SI unit. The footcandle is defined as 1 lumen per square foot, while lux is 1 lumen per square meter. Since 1 m² = 10.764 ft², 1 fc = 10.764 lx. Conversion: lux = footcandles × 10.764; footcandles = lux / 10.764. Common footcandle recommendations in US practice: offices 30–50 fc (320–540 lux); hallways 10–20 fc; retail stores 30–100 fc; operating rooms 500+ fc; outdoor roadways 0.5–2 fc; emergency exit lighting minimum 1 fc. US lighting standards (IES Lighting Handbook) specify footcandles, while European and international standards use lux. Photographers and cinematographers often work in footcandles or foot-lamberts in US production contexts.