Color Luminance Calculator
Calculate relative luminance of any color for WCAG contrast ratio compliance.
Contrast with white (#FFFFFF)
Contrast with black (#000000)
L = 0.2126 × Rs + 0.7152 × Gs + 0.0722 × Bs
Where Rs, Gs, Bs are linearized sRGB channels. Contrast ratio = (L1 + 0.05) / (L2 + 0.05). WCAG AA ≥ 4.5:1, AAA ≥ 7:1.
WCAG's contrast ratio between two colors is actually built from a more basic number first, each color's own relative luminance, a single value describing how much light a color effectively reflects, calculated by weighting its red, green, and blue channels unevenly since the eye reads green as far brighter than an equal amount of blue. This tool calculates a single color's relative luminance directly, showing the number the WCAG contrast formula is actually built from rather than the final ratio between two colors.
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Useful for understanding why a specific color is pulling a contrast ratio up or down more than its lightness alone would suggest, debugging a custom contrast-ratio implementation by checking its luminance calculation against a known value, or seeing which color channel is actually driving a shade's luminance number the most.
Key features
- Clean interface
- Fast processing
- No signup required
- Works offline