How color contrast checker works
Calculate WCAG contrast ratio for two opaque sRGB hex colors.
Formula and convention
Convert sRGB to relative luminance. Contrast = (lighter luminance + 0.05) / (darker luminance + 0.05).A worked example
The example dark green on white exceeds the 4.5:1 AA normal-text threshold.
Scope and precision
Three- or six-digit opaque hex only. AA normal text needs 4.5:1; AA large text 3:1; AAA normal text 7:1. This is not a full accessibility audit.
Displayed results may be rounded. Inputs are processed locally and are not stored by this site. Keep the original values if you need to reproduce the result.
Why might another tool give a different result?
Compare unit definitions, rounding, period assumptions, and input values. This page states the convention used by this calculator.