Kelvin tells you what color the light is, lumens how much light comes out. They are entirely independent: a 2700K spot and a 4000K spot can both give 400 lumens. When choosing lighting you need both numbers.
The two in one table
| Kelvin (K) | Lumens (lm) | |
|---|---|---|
| Tells you about | the color of the light | the amount of light |
| Low means | yellow, warm | little light |
| High means | blue, cool | plenty of light |
| Typical range at home | 2200K to 4000K | 320 to 700 per spot |
That last range comes from our own catalog: the Vigo sits at 320 lumens and the Lyvo reaches 700 on its high setting.
Why they get confused
Because you experience both as "how bright is it in here". But the sense of brightness comes from two sources: how much light there is and what color it is. Your eyes perceive warm light as less bright than cool light at the same quantity.
Put two 400-lumen spots side by side, one at 2700K and one at 4000K, and practically everyone points to the cool one as the brighter. A light meter sees no difference.
The order in which you choose them
Kelvin first, then lumens. That sounds arbitrary but it saves work:
- Settle your color temperature per room. 2700K for bedroom and seating area, 3000K for general use, 4000K above a worktop.
- Then work out the number of lumens. Roughly 100 to 150 lumens per square meter for a living room, 200 to 300 for kitchen and bathroom.
- Correct if you are going warm. If you choose 2700K everywhere, take the top of those ranges.
- Only then choose the spot. Divide the total by the output per unit.
Do it the other way round and you pick a lovely spot first, only to find it gives the wrong color or too little light.
Why watts is neither
There is a third number people bring into it: watts. That only tells you how much power a lamp uses, and since LED it says nothing about how bright it is. The Marlo uses 5 watts for 350 lumens, the Lyvo gets 500 lumens out of the same 5 watts. Same consumption, half as much light again.
In short: Kelvin for the color, lumens for the amount, watts for your energy bill.
Where the Kelvin scale comes from
The scale is not arbitrary. Kelvin is a unit of temperature, and the color matches how hot a piece of metal has to get to radiate that light. Heat metal and it glows red first, then yellow, then white and finally blue-white.
An incandescent bulb did literally that: heat a filament to about 2700 Kelvin. Which is why 2700K feels exactly like it used to. With LED nothing is heated, but the scale has stuck because everyone knows it by now. That also explains the confusing inversion: low Kelvin values are called warm and high ones cool, while physically it is the other way round.
Spots where you can still choose the Kelvin
The handy thing about a CCT switch is that you set the Kelvin value during installation while the lumen value is fixed. So you only have to make the first choice once the spots are in the ceiling:
- Lesto — 2700K/3000K/4000K, up to 400 lm, and 4 or 6 watts switchable too
- Quaro — 2700K/3000K/4000K, 400 lm
- Ferro — 2700K to 5700K, 600 lm
On the Lesto you can even adjust both numbers. That makes it a safe choice if you are not sure in advance how things will turn out.
In short
Two numbers, two questions. What atmosphere do I want here (Kelvin) and how much light do I need (lumens)? Answer them in that order and the rest follows. More about the calculation in How many lumens do you need per room? The full range is with the recessed spotlights.
Is more Kelvin more light?
No. More Kelvin is cooler, bluer light. How much light comes out you read from the number of lumens.
How many lumens is 3000K?
That question cannot be answered: 3000K is a color, not a quantity. Our 3000K spots run from 320 to 700 lumens.
Which do I choose first, Kelvin or lumens?
Kelvin. Settle the color per room, then work out the number of lumens, and only then choose the spot.