XYZ to Lab converter
Enter XYZ scaled so white Y = 100, pick the white the data was measured against, and get L*, a*, b*.
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Processing and privacy: The result is calculated inside your browser and your data is not sent to any server.
How to use it
- Enter x value, y value (relative luminance), z value and reference white of the data.
- The result appears straight away and updates as you edit.
- Copy the result, or copy a link that keeps the same values to share it.
How it is calculated
L* = 116 f(Y/Yn) − 16, a* = 500 (f(X/Xn) − f(Y/Yn)), b* = 200 (f(Y/Yn) − f(Z/Zn)), with f(t) = ∛t if t > 216/24389, else (24389/27 t + 16) / 116. Xn, Yn, Zn are the chosen white. No chromatic adaptation is applied.
Example
Inputs: X value = 41.2456, Y value (relative luminance) = 21.2673, Z value = 1.9334, Reference white of the data = D65 per ASTM E308 (95.047, 100, 108.883). Result: Lab values: L* 53.24, a* 80.09, b* 67.2; Lightness L*: 53.2408; a* (green to red): 80.0923.
Limits and caveats
- Choosing a white that does not match the measurement gives shifted Lab; the tool does not adapt between D65 and D50.
Questions about this tool
Which white should I pick?
Pick the white your sample was measured against. Instruments usually state D65/10° or D50/2°; the values here are for the 2° standard observer.
Why are there two versions of D65 and D50?
ASTM E308 tabulates the white from the full spectrum, while sRGB and ICC derive it from rounded x, y values, so the third digit differs.
What does 216/24389 do in the formula?
It is the CIE threshold for the linear segment near black, which avoids the steep cube root slope at very small values.