Lumens to Lux Calculator
Quick Conversions
Conversion Formula
Surface Area Method
Illuminance (lx) = Luminous Flux (lm) ÷ Area (m²)
E = Φ / A
One lux equals one lumen per square meter. This method calculates the average illuminance across a specified surface area.
Spherical Method
Illuminance (lx) = Luminous Flux (lm) ÷ (4π × r²)
E = Φ / (4π × r²)
This formula assumes the light source radiates equally in all directions. The illuminance decreases with the square of the distance from the source.
Beam Angle Method
Area = 2π × r² × (1 - cos(θ/2))
Illuminance (lx) = Luminous Flux (lm) ÷ Area
This method accounts for directional lighting with a specific beam angle, calculating the illuminated area on a spherical surface.
Conversion Examples
Example 1: Office Lighting
This illuminance level is suitable for general office work and casual reading areas.
Example 2: Flashlight at Distance
At 5 meters distance, a point light source provides minimal illuminance suitable for orientation in darkness.
Example 3: Spotlight with Beam Angle
A focused beam creates high illuminance suitable for detailed work or accent lighting.
Lumens to Lux Conversion Table
Common conversion values for a 10 m² surface area:
| Lumens (lm) | Area (m²) | Illuminance (lx) | Application |
|---|---|---|---|
| 200 | 10 | 20 | Outdoor construction site |
| 500 | 10 | 50 | Public areas, simple orientation |
| 1000 | 10 | 100 | Corridors, stairways, storage |
| 2000 | 10 | 200 | Break rooms, technical facilities |
| 3000 | 10 | 300 | Classrooms, libraries |
| 5000 | 10 | 500 | Office work, laboratories |
| 7500 | 10 | 750 | Supermarkets, workshops |
| 10000 | 10 | 1000 | Detailed mechanical work |
Distance vs Illuminance
How illuminance changes with distance for a 1000 lumen point source:
| Distance | Illuminance (lx) | Light Quality |
|---|---|---|
| 1 meter | 79.58 | Very bright, suitable for close work |
| 2 meters | 19.89 | Bright, good for general visibility |
| 3 meters | 8.84 | Moderate, adequate for movement |
| 5 meters | 3.18 | Dim, minimal visibility |
| 10 meters | 0.80 | Very dim, orientation only |
Recommended Lux Levels
According to EN 12464 standards for various environments:
| Activity/Location | Required Illuminance (lx) |
|---|---|
| Public areas with dark surroundings | 20 – 50 |
| Simple orientation for short visits | 50 – 100 |
| Corridors, stairways, storage areas | 100 |
| Warehouses, homes, theaters | 150 |
| Coffee rooms, waiting areas | 200 |
| Easy office work | 250 |
| Classrooms | 300 |
| Normal office work, PC work, study | 500 |
| Supermarkets, mechanical workshops | 750 |
| Detailed mechanical work, operation theaters | 1000 |
| Very detailed work, electronic workshops | 1500 – 2000 |
| Prolonged visual tasks of low contrast | 2000 – 5000 |
| Very prolonged and exacting visual tasks | 5000 – 10000 |
| Extremely low contrast and small size tasks | 10000 – 20000 |
What Are Lumens and Lux?
Lumens (lm)
Lumens measure the total amount of visible light emitted by a source. This represents the complete light output in all directions.
Higher lumen values indicate brighter light sources, regardless of where that light is directed.
Lux (lx)
Lux measures illuminance – the amount of light falling on a specific surface area. One lux equals one lumen per square meter.
Lux accounts for both distance and area, making it practical for evaluating actual lighting conditions.
Key Relationship
The same light source (fixed lumens) produces different lux values depending on distance and area. As light travels farther, it spreads over a larger area, reducing the lux value. A 1000 lumen bulb creates 100 lux at 10 m², but only 50 lux at 20 m².
Factors Affecting Lumens to Lux Conversion
Distance
Light intensity decreases with the square of the distance. Doubling the distance reduces illuminance to one-quarter of the original value.
Beam Angle
Narrow beam angles concentrate light into smaller areas, creating higher lux values. Wide beams spread light over larger areas with lower lux.
Surface Properties
Reflective surfaces can increase effective illuminance, while absorptive surfaces reduce it. Surface angle also affects actual light received.
Light Distribution
Real lights rarely distribute uniformly. Center beam areas typically have higher lux values than peripheral areas.
Related Light Measurement Units
- Candela (cd) – Luminous intensity in a specific direction, measured in candelas per steradian
- Lumens per Watt (lm/W) – Luminous efficacy, measuring how efficiently a light source converts power to visible light
- Foot-candles (fc) – Illuminance measurement in imperial units (1 fc = 10.764 lx)
- Nits (cd/m²) – Luminance measurement commonly used for displays and screens
- Lumen-hours (lm·h) – Total light energy over time, useful for battery-powered lights
- Color Temperature (K) – Kelvin measurement indicating the warmth or coolness of light appearance
Practical Applications
Residential Lighting
For living rooms, 150-300 lux provides comfortable ambient lighting. Kitchens and study areas require 300-750 lux for task lighting. Bedrooms function well with 100-200 lux for relaxation.
Commercial Spaces
Retail stores typically need 500-1000 lux to properly display merchandise. Office environments require 300-500 lux for computer work and 500-750 lux for reading and writing tasks.
Outdoor Lighting
Parking lots require 10-20 lux for safety. Pedestrian pathways need 5-10 lux. Sports facilities demand 200-500 lux depending on the activity level and competition requirements.
Photography and Videography
Professional photography studios often use 1000-2000 lux for even lighting. Video production typically requires 500-1000 lux minimum. Natural daylight provides 10000-25000 lux on cloudy days and up to 100000 lux in direct sunlight.
Frequently Asked Questions
How do I convert 1000 lumens to lux?
Divide the lumens by the area in square meters. For a 10 m² area: 1000 lm ÷ 10 m² = 100 lx. For point sources, use the spherical formula accounting for distance.
Why does the same bulb have different lux values?
Lux depends on both the light source and the receiving surface. The same bulb produces lower lux values at greater distances or over larger areas because the light spreads out.
What is the difference between lumens and lux?
Lumens measure total light output from a source, while lux measures the illuminance received on a surface. Lumens is a property of the light source; lux describes the lighting condition at a specific location.
How many lux do I need for reading?
Comfortable reading requires 300-500 lux. Older individuals or those with vision difficulties may prefer 500-750 lux. Prolonged reading sessions benefit from consistent, glare-free lighting at these levels.
Can I measure lux with my smartphone?
Many smartphones have ambient light sensors, and numerous apps claim to measure lux. However, these measurements are approximations. Professional lux meters provide accurate readings calibrated to lighting standards.
How does beam angle affect lux calculations?
Narrower beam angles concentrate light into smaller areas, creating higher lux values. A 10° spotlight produces much higher lux than a 60° flood light with the same lumens, because the light is focused rather than dispersed.
What is the relationship between distance and lux?
Illuminance follows the inverse square law: doubling the distance reduces lux to one-quarter. This exponential decrease means lighting effectiveness drops rapidly as distance increases from the source.
Are the calculator results perfectly accurate?
The calculator provides theoretical values assuming ideal conditions: uniform light distribution, no optical losses, and consistent source output. Real-world values vary due to fixture efficiency, environmental factors, and beam characteristics.
Tips for Choosing the Right Lighting
Match Lumens to Space Size
Calculate required lumens by multiplying your desired lux level by the area. A 20 m² room needing 300 lux requires 6000 lumens total from all light sources combined.
Consider Light Distribution
Multiple moderate sources often provide better illumination than one powerful source. Distributed lighting reduces shadows and creates more even illuminance across surfaces.
Account for Surface Reflectance
Light-colored walls and ceilings reflect light, effectively increasing illuminance. Dark surfaces absorb light, requiring higher lumen outputs to achieve the same lux levels.
Measure at Task Height
When evaluating workspace lighting, measure lux at the actual working surface – typically desk height (75 cm) rather than floor level. This provides relevant illuminance for the task at hand.