Lumens, Kelvin, and CRI, explained
How to read the box so you get the brightness and color of light you want.
Disclosure: We may earn a commission if you buy through links on this page. It does not change what we recommend. Affiliate Disclosure
Lumens: brightness
Lumens measure how much light a bulb gives off. Watts measure power used, not brightness. Use lumens to compare bulbs of any type.
| Old incandescent bulb | Look for at least |
|---|---|
| 40 W | 450 lumens |
| 60 W | 800 lumens |
| 75 W | 1,100 lumens |
| 100 W | 1,600 lumens |
Brightness in lumens
Built-in LED lamps list lumens for the whole lamp. Compare that number the same way.
Kelvin: color temperature
Color temperature describes how warm or cool white light looks. Lower numbers look warmer and more yellow; higher numbers look cooler and more blue.
| Kelvin | Look | Common use |
|---|---|---|
| 2,700 K | Warm | Living spaces, evening |
| 3,000 K | Soft white | Homes |
| 3,500 K | Neutral | Offices |
| 4,100 K | Cool | Offices, classrooms |
Color temperature
- 2,700 K
Warm - 3,000 K
Soft - 3,500 K
Neutral - 4,100 K
Cool
Words like "soft white" and "daylight" vary by brand. Trust the Kelvin number.
CRI: color accuracy
The Color Rendering Index rates how accurately a light shows colors, on a scale up to 100. ENERGY STAR bulbs must score at least 80. For art, crafts, or photo work, look for 90 or higher.
CRI scale, up to 100
The Lighting Facts label
In the US, most household bulb packages carry a Lighting Facts label showing brightness, estimated yearly energy cost, expected life, light appearance, and watts. Use it to compare.
Reading a Lighting Facts label
- Brightness (lumens)
- Estimated yearly energy cost
- Life
- Light appearance (Kelvin, warm to cool)
- Energy used (watts)
Matching the light to the room
A desk lamp far cooler or warmer than the room light can feel harsh. Many people choose a similar color temperature to the rest of the room, or a lamp with adjustable color.
FAQ
General information, not medical advice. See an eye care professional about eye strain or vision concerns.
