To know a lamp's light output accurately, don't look at watts alone—look at lumens, which measure the actual amount of light the lamp produces. Watts measure power consumption, while lumens measure the real brightness your eyes see.
Quick answer: Light output is measured in lumens (lm), and a lamp's efficiency in lumens per watt (lm/W). The higher the lm/W, the more light you get for less power.
Watts vs. lumens
- Watt: The electrical power the lamp consumes.
- Lumen: The actual amount of light the lamp produces (brightness).
We used to measure light by watts because old lamps had similar efficiency; with LED, lumens became the more accurate measure.
Luminous efficacy: lumens per watt (lm/W)
This is the key indicator of a lamp's power and efficiency. Rough examples:
- Incandescent: about 10–15 lm/W.
- Halogen: about 15–25 lm/W.
- CFL (energy saver): about 50–70 lm/W.
- LED: about 80–120 lm/W or more.
LED equivalents for traditional bulbs
- 40 W incandescent ≈ 5–6 W LED (about 450 lumens).
- 60 W incandescent ≈ 8–10 W LED (about 800 lumens).
- 100 W incandescent ≈ 12–15 W LED (about 1500 lumens).
How to read a lamp's power from the box
- Find the Lumen value for actual brightness.
- Check the Watt value for consumption.
- Read or calculate lm/W for efficiency.
- Check the color temperature (Kelvin) and CRI for light quality.
How many lumens does each room need?
It depends on the room's area and function. As a rough lux guide:
- Bedrooms and hallways: relatively soft lighting.
- Living rooms and kitchens: medium to high lighting.
- Work, reading, and task areas: high, focused lighting.
Rule of thumb: multiply the room area (m²) by the required lux to get approximate total lumens.
Tips for choosing the right power
- Don't rely on watts alone when buying LED.
- Spread light across several sources instead of one strong source.
- Use dimmable lamps to control brightness.
- Choose a CRI of at least 80 for natural colors.
Frequently asked questions
Do higher watts mean brighter light?
Not necessarily; watts measure consumption, brightness is measured in lumens. A lower-watt LED can be brighter than a higher-watt traditional bulb.
How many lumens equal a 60 W bulb?
About 800 lumens.
What's best for saving energy?
LED, because it delivers the highest lumens per watt and the longest lifespan.
Conclusion
A lamp's light output is measured in lumens, not watts, and its efficiency in lumens per watt. Read the box specs and calculate your need based on room area and function to choose the ideal power—saving energy and easing eye strain.
Shop LED lamps in various wattages and lumen outputs at Tirtk Lighting & Electrical