When it comes to lighting—whether for home, office, commercial spaces, or outdoor areas—two terms often cause confusion: lumen (lm) and lux (lx). These are critical metrics for choosing the right lighting that fits your needs, yet they measure entirely different aspects of light. Below is a clear guide to help you distinguish between lumens and lux, how to use them, and why they matter for your lighting decisions.
What is Lumen in Lighting?
Lumen (lm) is the unit used to describe luminous flux. In physics, it is defined as the total amount of light emitted within a solid angle by a source with a luminous intensity of one candela (cd, Candela—the unit of luminous intensity, roughly equal to the light from one ordinary candle).
In simple terms, lumen (lm) measures the total visible light output of a light source. Lumens focus on “how much light the source emits.”
Key Example: A 60W incandescent bulb emits ~800 lumens, while a 10W LED bulb (energy-efficient alternative) can produce the same or higher lumen count (800–1000 lm).
Why It Matters: Lumens tell you how “powerful” a light source is. When shopping for bulbs, focus on lumens (not watts) to ensure you get the desired brightness—watts measure energy consumption, not light output.
Common Uses: Comparing light fixtures, determining how much total LED light you need for a room (e.g., a living room may require 1,500–3,000 lumens total).
What is Lux?
Lux (lx) is the unit of illuminance, which measures light intensity per unit area—how much light actually reaches a surface (e.g., a desk, floor, or wall). It’s calculated as:
Lux = Lumens / Square Meters (m²)
Key Example: A 1000-lumen bulb shining on a 1m² desk produces 1000 lux. If the same bulb is moved to illuminate a 10m² room, the intensity drops to 100 lux.
Why It Matters: Lux tells you how “well-lit” a specific area is. Different activities and spaces require different lux levels to be functional and comfortable.
Common Lux Recommendations:
Casual living (e.g., bedroom, hallway): 100–300 lux
Office/workspaces (reading, computer work): 500–1000 lux
Task lighting (cooking, sewing, detailed work): 1000–2000 lux
Outdoor security lighting: 50–200 lux (motion-activated)
How to Estimate How Many Lumens You Need
To calculate the required lumens, you need to consider lux, the illuminated area, and fixture efficiency. The basic formula is:
Required Lumens = Lux × Area (m²)
For example, if a 10 m² room needs 500 lx of illuminance, the calculation is:
| Parameter | Number |
| Lux | 500 |
| Illuminated Area | 10 m² |
| Required lumen | 5000 |
In practice, you also need to consider the fixture’s luminous efficiency and light distribution, which may result in selecting a higher wattage than the theoretical value.
EN12464 Lux Level Chart
Factors Affecting Lux and Lumens
Lux (light intensity per unit area) is primarily influenced by 6 core factors, all tied to its definition: Lux = Lumens (total light output) / Square Meters (irradiated area). Below is a clear, practical breakdown for easy understanding:
- Total Light Output of the Source (Lumens)
- Irradiated Area (Square Meters)
- Distance Between Light Source and Surface
- Light Directionality (LED Light Beam Angle)
- Obstacles or Blockages
- Reflectivity of Surrounding Surfaces
Lumens are mainly determined by the LED chips used, and the packaging process also plays a role. In general, higher wattage produces higher lumens, but when choosing lighting products, you should focus on lumens, not wattage.
How to choose the right lighting fixtures?
Determine the target area → Calculate the illuminated area → Set the target lux level → Calculate the required lumens → Consider fixture efficiency → Choose suitable lighting fixtures.
Following this process allows you to systematically complete the entire workflow from requirement analysis to fixture selection.
Common types of LED lighting fixtures include:
Indoor lighting fixtures: LED downlight, track light, panel light, linear light, strip, high bay LED lights, wall lights, floor lights.
Outdoor lighting fixtures: floodlights, bollard lights, street lights
Frequently Asked Questions
No, 5000lux means the intensity of light illuminating a specific surface. 5000 lumens represent the total amount of visible light emitted by a lamp.
Yes, it is bright enough. Direct sunlight provides about 100,000 lux, while a cloudy day provides around 1,000 lux only, now you can see.
1 lux means there is one lumen evenly distributed over 1 square meter of surface area.
- Use a lux meter; just place the lux meter at the point you want to measure (e.g., on a desk or floor).
- Use a mobile App, such as Lux Meter, Light Meter apps, but accuracy is lower
Hello, customers
My name is Ricky Wang, I’m the business manager of GRNLED. I have been in LED lights industry for more than 10 year. Feel free to contact us. I’m happy to provide you the best service and products.
Email: info@grnled.com | WeChat: ledfixture
