What does that colour temperature look like?
Colour temperature runs backwards from intuition: higher numbers are bluer, and blue is what we call cool.
Almost exactly a neutral white LED
4,000 K is cooler than 4 of the 9 references on this page.
Reference figures are measurements and are rounded; the unit conversion behind them is exact.
| Reference | Size | Yours ÷ theirs | Note |
|---|---|---|---|
| candle flame | 1,900 K | 2.11× | |
| sunrise and sunset | 2,000 K | 2× | |
| incandescent bulb | 2,700 K | 1.48× | Warm white |
| halogen | 3,000 K | 1.33× | |
| neutral white LED | 4,000 K | 1× | |
| midday sunlight | 5,500 K | 0.727× | |
| camera flash | 5,500 K | 0.727× | |
| overcast daylight | 6,500 K | 0.615× | Cool white |
| clear blue sky | 10,000 K | 0.4× |
Worth knowing
- Colour temperature is the temperature a black body would have to be to glow that colour, which is why the scale runs the wrong way round.
- Domestic lighting in Europe clusters at 2 700 K and in much of Asia at 6 500 K, purely by convention.
Frequently asked
Is warm white or cool white better?
Warm white, around 2 700 K, suits living spaces and evenings because it matches the light people are used to relaxing in. Cool white suits task areas and daylight-matched work.
Why is higher kelvin called "cool"?
Because of how the colour feels, not the physics. A 6 500 K light is genuinely hotter as a black body and looks bluer, which we read as cold.