Quick Lumen ⇄ Lux Converter
Use this lighting calculator to convert lumens to lux (or lux to lumens) based on the illuminated area.
What is the difference between lumens and lux?
People often use lumens and lux as if they are the same thing, but they measure different parts of lighting:
- Lumens (lm) measure total light output from a source.
- Lux (lx) measures how much of that light falls on a surface area.
In plain language: lumens tell you how much light a bulb emits, while lux tells you how bright a specific spot actually appears.
How the lumen to lux formula works
The core formula is simple:
Lux = Lumens ÷ Area (in m²)
And the reverse:
Lumens = Lux × Area (in m²)
If your area is in square feet, convert first:
1 ft² = 0.092903 m²
How to use this calculator
For lumen to lux
- Select Lumens → Lux.
- Enter total lumens from your lamp or fixture.
- Enter the illuminated area and unit.
- Click Calculate to get lux.
For lux to lumen
- Select Lux → Lumens.
- Enter your target lux level.
- Enter room/task area and unit.
- Click Calculate to estimate required lumens.
Typical lux recommendations
These are common starting points for interior lighting design:
- Hallways: 50–100 lux
- Living rooms: 100–300 lux
- Kitchens: 300–500 lux
- Office desks: 300–750 lux
- Detailed tasks (drafting, lab work): 750–1500 lux
Final targets depend on age, visual comfort, reflectance, fixture placement, and local standards.
Worked examples
Example 1: 1200 lumens over 10 m²
Lux = 1200 ÷ 10 = 120 lux. Good for general ambient lighting in a relaxed room.
Example 2: Need 500 lux for a 8 m² workspace
Lumens = 500 × 8 = 4000 lumens. You can achieve this with one high-output fixture or multiple combined sources.
Common mistakes to avoid
- Using floor area when only part of the space is actually lit.
- Ignoring fixture losses, shades, or dirty lenses.
- Confusing initial lumens with maintained lumens over time.
- Forgetting to convert ft² to m² before applying lux formulas manually.
Frequently asked questions
Is lux the same as brightness?
Lux is a physical measurement of illuminance. Human perception of “brightness” also depends on contrast, color temperature, adaptation, and surface reflectivity.
Can I use this for outdoor lighting?
Yes. The math is the same, but outdoor design usually needs extra allowances for spill, uniformity, weather conditions, and safety codes.
Does beam angle matter?
Absolutely. The same lumens concentrated in a narrow beam can produce much higher lux at the target than a wide beam.
Bottom line
A lumen to lux calculator helps you move from “how much light a fixture makes” to “how much light reaches the task.” Use it when planning room lighting, office setups, workshop illumination, photography spaces, and energy-efficient upgrades.