Choosing the right light bulb: Understanding everything from lumens to watts and kelvins

Converting watts to lumens and other lighting characteristics

When shopping for light bulbs or considering your lighting needs, you’ve likely encountered the terms “lumens,” “watts,” and “kelvins.” While these measurements are often used in discussions about lighting, they describe very different characteristics. Understanding how to convert watts to lumens and what is meant by colour temperature (measured in kelvins), can help you make informed decisions about the lighting in your home or workspace.

1. What is a watt?

A watt (W) is a unit of power that measures the energy consumption of a light bulb. Traditionally, it was the go-to metric for gauging a light bulb’s brightness because incandescent bulbs’ brightness correlated closely with their wattage. A 60-watt incandescent bulb, for example, was brighter than a 40-watt bulb.

However, with the rise of energy-efficient lighting technologies like LEDs and CFLs, wattage no longer provides an accurate indication of brightness. Modern bulbs use far less power to produce the same amount of light as traditional bulbs, making lumens to watts conversion a more relevant factor for understanding energy-efficient lighting.

2. What Is a lumen?

Lumens (lm) measure the amount of visible light a bulb emits. In simple terms, it’s a measurement of brightness. The higher the lumen rating, the brighter the light.

For example:

• A 450-lumen bulb emits roughly the same brightness as a 40-watt incandescent bulb.
• A 1600-lumen bulb is comparable to a 100-watt incandescent bulb.

Since lumens are a direct measure of brightness, they have become the standard for comparing lighting options across different types of bulbs. This makes lumens to watts conversion essential for choosing the right lighting.

Understanding the difference between lumens and watts also allows you to choose lighting that meets your needs while saving energy. For example, if you want a bright workspace, look for bulbs with higher lumens. If energy efficiency is your goal, compare bulbs with lower wattage for the same lumen output.

3. What are kelvins?

Now you know how to measure the brightness of your bulb but what about the colour? Kelvins (K) refer to the colour temperature of light, which influences the mood and functionality of a space. The lower the Kelvin rating, the warmer (more yellow) the light appears; the higher the Kelvin rating, the cooler (more blue) the light appears.

• 2700K-3000K: A warm light with a yellowish tone. Best for cosy, relaxing spaces like bedrooms and living rooms.
• 3500K-4000K: A neutral white light. Ideal for kitchens, bathrooms, and offices where a balance between warm and cool light is needed.
• 5000K-6500K: A cool white light that mimics daylight. Perfect for workspaces, garages, and areas requiring bright, focused lighting.