Color Luminance Calculator

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. 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.