Color Temperature Converter
Convert a colour temperature in kelvin to its RGB value and back, with the common lighting references, the white balance a photograph needs, and the CSS for a warm display filter.
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Warm light has a low number
The naming is backwards from how it feels. A candle at 1900K is described as warm and an overcast sky at 7000K as cool, yet the physical temperature runs the other way: the higher number is genuinely hotter. The scale comes from heating an idealised black body and recording the colour it glows, so a hotter object glows bluer. Everyday language attached warm to orange and cool to blue independently, and the two conventions have been in conflict ever since.
White balance is the inverse
A camera set to 5500K under 3000K tungsten lighting records everything with an orange cast, because it expects bluer light than it receives. Correcting means telling the camera the light is 3000K, at which point it applies the opposite shift and the whites come out white. The white balance setting is not the colour you want; it is the colour of the light you are cancelling, which is why raising the number warms the image rather than cooling it.
Screen temperature affects sleep, modestly
Evening display filters shift the screen towards 2700K or lower on the basis that blue light suppresses melatonin. The effect exists and is smaller than the popular framing suggests, and studies comparing filtered and unfiltered evening screen use find modest differences at best. Total screen time and what you are doing on it matter more than the colour temperature, and a warmer screen is easier on the eyes in a dim room regardless of what it does for sleep.
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Frequently Asked Questions
Why is a lower kelvin called warm?
Because everyday language attached warm to orange light independently of the physics. The scale measures the temperature of an idealised glowing body, where hotter genuinely means bluer, so the two conventions run in opposite directions.
What temperature is daylight?
Around 5500K to 6500K for midday sun, higher under an overcast sky and higher still in open shade, which can exceed 8000K. Sunrise and sunset drop to 2000K or below, which is why photographs at those times look orange.
Why does raising white balance warm my photo?
Because the setting describes the light you are cancelling, not the result you want. Telling the camera the light is warmer makes it apply a stronger blue correction in the opposite direction, warming the recorded image.
Do blue light filters improve sleep?
The effect on melatonin is real and smaller than the popular framing suggests. Studies comparing filtered and unfiltered evening screen use find modest differences, and total screen time matters more than the colour of it.
Is this conversion exact?
No. It uses a well-known published approximation that is accurate to a few percent between roughly 1000K and 40000K. An exact conversion requires the full black body spectrum and the colour matching functions, and the difference is not visible for practical use.
Privacy & Security
Everything runs in your browser; nothing is uploaded.
How to Use
Enter a temperature in kelvin to see the colour it produces and what it corresponds to.
Disclaimer: This tool is provided "as is" without warranty of any kind. Results are for educational and utility purposes.
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