Use this Lab, LCh and XYZ converter to move between common CIE color spaces from spectrophotometer readings. The calculation is local to your browser. For a color difference between two Lab readings, use our Delta E Calculator.
What are XYZ, Lab and LCh?
CIE XYZ represents a color using three tristimulus values. Instruments derive these values from measured spectral data using a specified illuminant and standard observer.
CIELAB expresses color as lightness (L*), a green–red axis (a*) and a blue–yellow axis (b*). The Lab coordinates are calculated relative to a reference white, so the chosen illuminant and observer must match the conditions associated with the data.
CIELCh describes the same Lab color with lightness (L*), chroma (C*ab) and hue angle (h°ab). Chroma indicates distance from neutral; hue angle describes direction around the a*–b* plane. LCh can make a measured color shift easier to describe in production.
Choose the right reference white
A reference white defines the illuminant and observer white used to calculate Lab from XYZ. D65 is commonly used for daylight-related and sRGB work, while D50 is common in print workflows. The 2° and 10° settings refer to CIE standard observers. Selecting a different reference white changes the Lab and LCh coordinates calculated from XYZ.
For comparisons, use the illuminant, observer and measurement settings specified by your instrument, customer or process. XYZ values from different measurement conditions are not automatically comparable just because they use the same three letters.
How to use the converter
- Choose the reference white and observer that match your measurement data.
- Enter the three coordinates in XYZ, Lab or LCh. The other two sets update as you type.
- Copy the converted coordinates for a worksheet, specification or color workflow.
XYZ inputs use a 0–100 scale, where a normalized reference white has Y = 100. Lab lightness is entered from 0 to 100. The hue angle is in degrees.
What this conversion does not tell you
The converter transforms numeric coordinates. It does not recreate a physical sample on a screen, calculate XYZ from a spectral reflectance curve, or predict how a fluorescent, textured or glossy material will appear under another light source. Those tasks need the underlying spectral data and the right instrument settings.
If you want a screen-based starting point, our HEX, RGB, HSL and CMYK color converter handles display color formats. Its RGB and CMYK values are not a substitute for instrument measurements.
Lab, LCh and XYZ conversion FAQ
What is the difference between Lab and LCh?
LCh is a cylindrical form of Lab. It keeps the same lightness, then expresses the a* and b* axes as chroma and a hue angle. The color coordinates describe the same color when calculated using the same reference white.
Why does changing D50 to D65 change my Lab values?
Lab is calculated relative to a reference white. D50 and D65 represent different standard illuminants, so XYZ coordinates interpreted against those whites produce different Lab and LCh coordinates.
Does this converter upload my color data?
No. The coordinate conversions run in your browser. The page does not send the values to a server or save them in browser storage.