Color Temperature to RGB
Convert a light color temperature in Kelvin (1000K–12000K) to an approximate RGB color, as used in photography and lighting design.
How to use this tool
- Enter a color temperature in Kelvin (1000–12000).
- The tool uses the Tanner Helland algorithm to approximate the RGB color.
- Common values: 2700K (incandescent), 4000K (cool white), 6500K (daylight).
Convert light color temperature (Kelvin) to an approximate RGB value. Warm candlelight is ~2000K, daylight is ~6500K, and a blue sky can be 10000K+.
Formula
The conversion uses Tanner Helland's piecewise empirical approximation. Let temp = K / 100 (where K is clamped to 1000–12000).
Red: If temp ≤ 66 then R = 255; else R = 329.699 × (temp − 60)−0.1332
Green: If temp ≤ 66 then G = 99.471 × ln(temp) − 161.120; else G = 288.122 × (temp − 60)−0.0755
Blue: If temp ≥ 66 then B = 255; if temp ≤ 19 then B = 0; else B = 138.518 × ln(temp − 10) − 305.045
All channels are clamped to [0, 255] and rounded to integers.
How it works
The algorithm divides the Kelvin scale into regions and fits separate power-law and logarithmic curves to each RGB channel, approximating the spectral power distribution of a blackbody radiator. The result is an sRGB triplet that represents how a human eye perceives light of that color temperature, suitable for white-balance simulation and lighting design software.
A common mistake is assuming the output is perceptually linear: at 6600 K the three channels all read 255 (pure white), because 6500–6600 K is the conventional daylight white point — values above and below shift toward blue or warm-orange respectively, not symmetrically.
Worked example
Convert 6600 K (daylight white point) to RGB
- Input: kelvin = 6600 K, so temp = 6600 / 100 = 66.
- Red: temp = 66, which satisfies temp ≤ 66, so R = 255.
- Green: temp = 66, which satisfies temp ≤ 66, so G = 99.471 × ln(66) − 161.120 ≈ 254.97 → rounded to 255.
- Blue: temp = 66, which satisfies temp ≥ 66, so B = 255.
rgb(255, 255, 255) — R: 255, G: 255, B: 255, Hex: #ffffff
Common mistakes to avoid
- Using a Kelvin value below 1000 K or above 12000 K, which is outside the empirical fit range and produces clamped, inaccurate RGB output.
- Expecting photometrically accurate color science from this piecewise approximation -- it is a display approximation, not CIE chromaticity data.
- Confusing correlated color temperature (CCT) with tint (green-magenta axis) -- this calculator only models the CCT axis, not full white-point matching.
Key terms
- Color temperature (K)
- A measure of the spectral character of light, expressed in Kelvin. Lower values (1800–3000 K) appear warm/orange; higher values (6000–8000 K) appear cool/blue-white.
- Blackbody radiator
- A theoretical object that emits light purely as a function of its temperature. The color of an incandescent light source approximates a blackbody spectrum.
- sRGB
- The standard Red-Green-Blue color space used by most monitors and web content. Each channel is an integer from 0 to 255.
- Daylight white point (D65)
- The standard reference for neutral white light, defined at approximately 6500 K. Camera white-balance and display calibration are commonly referenced to this point.
Frequently asked questions
- What is color temperature?
- Color temperature describes the hue of a light source on a scale from warm (reddish, low Kelvin) to cool (bluish, high Kelvin). It comes from blackbody radiation physics.
- Is this conversion exact?
- No — it is an approximation by Tanner Helland (2012) that gives perceptually good results for the visible daylight range. Exact conversion requires spectral power distribution data.