Luminance Converter

The Luminance Converter turns a colour into the numbers that describe how bright it really is, then tells you whether two colours have enough contrast to be readable.

Brightness is not a single idea: the tool reports three measures so you can pick the right one.

Relative luminance follows the WCAG definition, linearising each sRGB channel before applying the standard 0.2126 / 0.7152 / 0.0722 weights, and it is the value used in accessibility contrast checks.

Perceived luma applies those same weights to the raw gamma-encoded values for a quick approximation, while the channel average is the plain mean of red, green and blue.

Green contributes far more to perceived brightness than red, and red far more than blue, which is why a pure green looks lighter than a pure blue of the same numeric intensity — the weighted measures capture exactly that.

Pick a second colour and the tool computes the WCAG contrast ratio between the two, from 1:1 up to 21:1, and labels it against the AA and AAA thresholds for normal and large text.

That makes it easy to confirm that body copy, buttons and links will be legible.

Everything is calculated locally in your browser with no uploads, so it is fast, private and works offline once loaded.