Luminous flux (lm) vs. power (W): how to read the technical data correctly
When choosing a light or bulb today, it is no longer enough to look at "watts". Modern lighting, especially LED technology, has brought new concepts that are key to making the right choice. Among the most important are luminous flux and wattage (power).
What exactly do they mean, how do they differ and how to use them correctly when choosing lighting? Let's explain it simply and clearly.
What is luminous flux (lm)
Luminous flux indicates how much light the source actually emits.
This is the most important figure if you want to know how much the room will be illuminated.
- Specified in lumens (lm)
- The higher the lumen value, the more light
- No matter the technology (incandescent, LED, fluorescent)
Practical example
- 400 lm → night lamp, orientation light
- 800 lm → common replacement for old 60W bulb
- 1500-2000 lm → powerful ceiling or work lighting
Luminous flux tells how much light actually "shines".- A simple tool.
What is power (W)
Power (wattage) indicates how much electricity the light source consumes.
- Specified in watts (W)
- It doesn't say how much light the source puts out
- Mainly used to determine electricity consumption
Important notice
For classic light bulbs: more watts = more light
This is no longer the case with LED lighting.
For example:
- 8 W LED can shine as well as an old 60 W bulb
Power tells you how much electricity you pay, not how much it will shine.- A simple tool.
The main difference between luminous flux and power
|
Parameter |
What does it express |
Unit |
What is it used for |
|---|---|---|---|
|
Luminous flux |
Amount of light |
lumen (lm) |
How much the light shines |
|
Power |
Energy consumption |
watt (W) |
How much electricity does it consume |
How do I know the difference when I buy?
❓ What should I look at first?
➡️ Per lumens (lm)
This is the figure that tells you whether the light will be strong enough.
❓ So what are watts for?
➡️ To compare consumption and efficiency
Lower watts at the same lumens = more efficient light.
❓ Why does an LED have few watts but many lumens?
➡️ LED technology has high luminous efficiency - it produces more light from less energy.
Recommended luminous flux values by room
|
Room |
Recommended luminous flux |
|---|---|
|
Corridor |
100-150 lm/m² |
|
Living room |
150-250 lm/m² |
|
Kitchen |
300-500 lm/m² |
|
Workroom |
400-600 lm/m² |
|
Bathroom |
300-500 lm/m² |
Always think about multiple light sources - ceiling, supplementary, working.- Tip from 360design.
Customer FAQs
❓ Does more lumens always mean better light?
Not necessarily. It also depends on:
- chromaticity temperature (colour of light)
- direction of light
- glare and shading
❓ Why do two lights with the same lumens shine differently?
The difference may be in:
- angle of emission
- quality of optics
- light colour (warm vs. cold)
❓ Which parameter is the most important today?
➡️ Luminous flux (lm) + efficiency (lm/W)
This tells you how much light you get for how much energy.
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