What happens when Whiteness + Blackness exceed 100%?

The HWB spec normalizes the two components proportionally so they sum to 100%. This tool applies the same normalization, which produces an achromatic (gray) color.

Which LAB illuminant does this tool use?

The conversion uses the CIE Standard Illuminant D65, which is the reference white for sRGB and the most common choice for web and screen work.

How accurate is the conversion?

The conversion follows the IEC 61966-2-1 sRGB spec and the standard CIE LAB formulae. Results match professional color tools to within rounding error on the last decimal.

What do the a* and b* axes mean?

In CIE LAB, a* runs from green (negative) to red/magenta (positive), and b* runs from blue (negative) to yellow (positive). L* is lightness from 0 (black) to 100 (white).

Can I go from LAB back to HWB?

This tool is one-directional. For the reverse, use a LAB to HWB converter which applies the inverse pipeline (LAB → XYZ → linear RGB → sRGB → HWB).

HWB to LAB Converter

Enter HWB color values and instantly see the equivalent CIE LAB (L*, a*, b*) values with a live color swatch.

HWB Input

Hue (0 – 360°)

Whiteness (0 – 100%)

Blackness (0 – 100%)

#47A0C8

CIE LAB Result

62.72

−12.41

−27.58

Intermediate Values

RGB rgb(71, 160, 200)

XYZ (D65) X 0.3012 Y 0.3512 Z 0.5944

Normalized W+B W 20% + B 10%

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Summary

This tool converts colors specified in the HWB (Hue, Whiteness, Blackness) model into the CIE LAB color space (also written L*a*b*). HWB is an intuitive cylindrical model where you mix a pure hue with white and black pigment. CIE LAB is a device-independent, perceptually uniform space widely used in color science, print production, and image processing. The conversion pipeline goes HWB → RGB → linear RGB → XYZ (D65) → LAB.

How it works

Enter the Hue (0–360°), Whiteness (0–100%), and Blackness (0–100%) values.
The tool normalizes HWB to RGB by blending the hue's pure color with white and black components.
RGB values are linearized (gamma expanded) then converted to CIE XYZ using the sRGB D65 matrix.
XYZ coordinates are adapted to the D65 illuminant and transformed into CIE LAB (L*, a*, b*).
Results are displayed instantly alongside a live color swatch and the intermediate hex and RGB values.

Use cases

Convert designer HWB color picks into LAB for perceptual color difference (ΔE) calculations.
Prepare color data for print workflows that require LAB input.
Validate color space round-trips during UI or brand color system development.
Explore how lightness (L*) and chroma (a*, b*) change as you add white or black to a hue.
Cross-reference HWB values from CSS Color Level 4 with scientific LAB references.
Quick color conversion without installing desktop software.

Frequently Asked Questions

Last updated: 2026-05-28 · Reviewed by Nham Vu