RGB & CIELab Color Converter

What this RGB to CIELAB converter returns

Use the converter to move between an 8-bit sRGB color and CIE L*a*b* (CIELAB) coordinates. Enter a HEX color, choose a preset, or adjust the RGB controls; the page updates the color preview and corresponding values. Adjusting the Lab controls works in the reverse direction and returns an sRGB color. The RGB channels use integer values from 0 to 255. The Lab controls allow L* from 0 to 100 and a* and b* from −128 to 127, with 0.1 steps.

L* describes lightness; a* runs from greenish negative values toward reddish positive values; b* runs from bluish negative values toward yellowish positive values. These are coordinates, not separate red, green, and blue channels.

Reference white changes the answer

CIELAB coordinates are calculated relative to a specified reference white. This converter follows an sRGB to XYZ path using D65 and the D65 reference white constants in its calculation. A “Lab” value from another program may use a different RGB profile or reference white, so the same displayed color can produce different coordinates. The CIE definition is based on XYZ tristimulus values and a specified white stimulus.

For each normalized XYZ component, the CIELAB calculation applies a piecewise function f. The coordinates are L* = 116f(Y/Yn) − 16, a* = 500[f(X/Xn) − f(Y/Yn)], and b* = 200[f(Y/Yn) − f(Z/Zn)]. Here Xn, Yn, and Zn identify the reference white.

Use the controls for a color match check

Start with the HEX value if you have a color from a website or design file. A valid HEX value updates RGB, Lab, and the preview together. If the text is not yet a valid color, the current valid result remains until the input parses.

Use the RGB controls when you need exact integer channel values. Use the Lab controls when you want to explore lightness or the green–red and blue–yellow axes. The displayed RGB is rounded to whole channel values, while Lab results from RGB are shown to two decimal places.

A practical sequence for converting a color

1. Load the source color

   Enter a valid HEX color such as #3B82F6, select a preset, or open the color picker. Check the preview to confirm you have the intended source.

2. Read or refine coordinates

   Read the linked RGB and Lab values, or move an RGB slider in whole-number increments. For a Lab target, adjust L*, a*, or b* in 0.1 increments and observe the resulting sRGB color.

3. Copy the needed format

   Copy the HEX value, RGB expression, an individual Lab coordinate, or the complete result. Keep the reference-white and input-space assumptions with the copied Lab numbers when sharing them.

For example, a blue-looking color often has a negative b* coordinate, while a nearly neutral gray tends to have a* and b* nearer zero. Treat this as an interpretation aid rather than a color measurement.

Questions about RGB and Lab values

Limits to keep in mind

• Lab values can describe colors outside the sRGB gamut. When converting back, RGB channel values are clipped to 0–255 and rounded to integers, so the returned RGB may not reproduce the original Lab target.
• The a* and b* slider endpoints are this page’s input limits, not universal mathematical limits of CIELAB.
• Two-decimal display precision and integer RGB output do not establish measurement accuracy. Screen appearance also depends on display and viewing conditions.
• For print, product, or instrument color decisions, align profiles, reference conditions, and a specified color-difference method with the relevant workflow.