XYZ → CIE 1931 xyY
Enter CIE tristimulus values (X, Y, Z). This computes chromaticity coordinates x and y, plus an estimated correlated color temperature (CCT).
sRGB → XYZ and CIE 1931 xy
Use RGB values (0–255) or a hex color. Assumes standard sRGB with D65 white point.
What is a CIE 1931 calculator?
The CIE 1931 color space is one of the most widely used systems for describing color numerically. A CIE 1931 calculator helps you convert between common color values (like RGB or XYZ) and chromaticity coordinates x and y. Those coordinates represent a color independent of brightness, which makes comparison and communication much easier.
In practice, this is useful for display calibration, LED binning, camera characterization, colorimetry labs, and anyone working with color science tools.
How this calculator works
1) XYZ to xyY
If you already have tristimulus values X, Y, and Z, the calculator computes:
x = X / (X + Y + Z)y = Y / (X + Y + Z)Yis carried through as luminance
This separates chromaticity (x, y) from brightness (Y), which is the core idea behind the xyY representation.
2) sRGB to XYZ to xy
When you input sRGB values, the calculator first linearizes gamma-corrected RGB, then applies the standard sRGB-to-XYZ transform matrix (D65 reference white). Finally, it computes xy coordinates from XYZ.
This means the result matches common web and display workflows, provided your source values are true sRGB.
Why CIE 1931 still matters
Even though newer color models exist, CIE 1931 remains a baseline in standards, spec sheets, and measurement devices. Most color quality workflows still reference xy coordinates at some point. Common use cases include:
- Comparing LED chromaticity from datasheets
- Checking white-point drift in displays
- Evaluating color consistency in manufacturing
- Converting camera and sensor responses into standard spaces
Interpreting your results
Chromaticity (x, y)
The x and y values describe hue and saturation location in the CIE 1931 diagram. Nearby points appear visually similar under standard assumptions.
Luminance (Y)
The Y value corresponds to luminance contribution in XYZ. Two colors can share the same x and y but have different Y, meaning same chromaticity but different brightness.
Estimated CCT
The calculator includes a quick correlated color temperature estimate using McCamy’s approximation. It is handy for quick checks, but should not replace high-accuracy CCT methods when precision is critical.
Practical tips for reliable calculations
- Use linear-light data when possible; gamma-encoded values can be misleading if not converted properly.
- Keep track of your illuminant and observer assumptions (e.g., D65 and 2° standard observer).
- Don’t compare xy results from one pipeline to XYZ from another without confirming transforms.
- Remember that out-of-gamut RGB values can produce unusual chromaticity behavior.
Example workflow
A quick display-check workflow might look like this:
- Read a target patch from your display as RGB.
- Convert RGB to XYZ using known profile assumptions.
- Convert XYZ to xy and compare against target chromaticity.
- Adjust calibration until the measured xy falls within tolerance.
Limitations to keep in mind
No lightweight web calculator can replace a full spectral model. CIE 1931 xy is incredibly useful, but it does not encode all perceptual behavior, adaptation effects, or metameric differences. For engineering-grade work, always pair chromaticity calculations with controlled measurement conditions and appropriate standards documentation.
Final thoughts
If you need quick, practical color math, a CIE 1931 calculator is one of the best tools to keep nearby. Use it to move between RGB, XYZ, and xy coordinates, spot obvious errors fast, and communicate color intent clearly across software, hardware, and teams.