Color to LAB

What is the LAB color space?

CIE LAB (also written L*a*b*) is a device-independent color space defined by the International Commission on Illumination (CIE) in 1976. It was designed to be perceptually uniform — meaning a change of the same numeric amount should look roughly equally different to a human eye across the whole space. The three channels are Lightness (L*), the green–red axis (a*) and the blue–yellow axis (b*).

L* runs from 0 (black) to 100 (white). Positive a* is red, negative a* is green. Positive b* is yellow, negative b* is blue. Because LAB separates lightness from color, it is the workhorse of professional color management: it can represent every color the human eye can see, and edits to one channel do not disturb the others the way RGB edits do.

How RGB is converted to LAB

The conversion goes through three steps. First, the sRGB values are linearized to remove the display gamma. Then linear RGB is transformed to CIE XYZ using the D65 standard illuminant matrix. Finally XYZ is mapped to LAB using a non-linear cube-root function and a reference white point:

R' = ((R/255 + 0.055) / 1.055)2.4 (linear RGB)
X = 0.4124·R' + 0.3576·G' + 0.1805·B' (XYZ, D65)
Y = 0.2126·R' + 0.7152·G' + 0.0722·B'
Z = 0.0193·R' + 0.1192·G' + 0.9505·B'
L = 116·f(Y/Yn) − 16, a = 500·(f(X/Xn) − f(Y/Yn)), b = 200·(f(Y/Yn) − f(Z/Zn))

where f(t) = t^1/3 for t > 0.008856, otherwise 7.787·t + 16/116, and (X_n, Y_n, Z_n) is the D65 reference white. This tool performs all of that math live as you pick a color.

When to use LAB

LAB is the right choice whenever perceptual accuracy matters more than screen or print convenience:

• Color difference. The Euclidean distance between two LAB colors approximates perceived difference, so LAB powers ΔE tolerance checks.
• Color correction. Photo editors move the L* channel for brightness without shifting hue.
• Gamut mapping. Converting between RGB and CMYK often routes through LAB as a common, wider space.
• Pantone matching. Brand color systems report LAB alongside HEX/CMYK for cross-medium consistency.
• Accessibility. Perceptual lightness L* is closer to human perception than relative luminance.

For day-to-day web work, HEX and RGB remain more convenient because CSS accepts them directly — LAB only recently landed in CSS as lab().

LAB vs RGB, HEX and CMYK

RGB and HEX describe colors a screen can emit; CMYK describes ink a printer can lay down. LAB describes a color as a human would perceive it under a defined light source, independent of any device. That makes LAB the largest of the four spaces — it contains colors no monitor or printer can reproduce. Converting RGB to LAB never loses information; converting LAB back to RGB clips out-of-gamut values.

Because LAB is perceptually uniform, two colors with the same L* look equally bright, and two colors the same numeric distance apart look about equally different — properties RGB and CMYK do not have.

How to convert a color to LAB

Converting a color to LAB with this tool takes a second and runs entirely in your browser. No upload, no sign-up, no install. Follow these steps:

1. Pick a color. Use the color picker, or type red, green and blue values (0–255) into the RGB inputs.
2. Read the result. The L*, a*, b* values and the full lab() string update live.
3. Copy LAB. Click "Copy LAB" to copy the value, then paste it into your color management tool or design app.

Every step runs locally in JavaScript, so your color choice never leaves your browser. This makes the tool completely private and instant.