Contrast Checker (WCAG)

The WCAG contrast ratio is calculated using relative luminance (L1 and L2): (L1 + 0.05) / (L2 + 0.05), where L1 is the lighter color relative luminance and L2 is the darker color relative luminance. The resulting ratio ranges from 1:1 (zero contrast, e.g. white on white) to 21:1 (maximum contrast, black on white).

Level AA is the standard legal baseline for most web accessibility regulations (including ADA and Section 508). It requires a minimum 4.5:1 ratio for normal text and 3.1:1 for large text. Level AAA is the highest accessibility level, requiring 7.0:1 for normal text and 4.5:1 for large text.

Under WCAG guidelines, "Large Text" is defined as font sizes 18pt (24px) or larger for regular weight text, OR 14pt (approx. 18.66px) or larger for bold text.

Yes! Under WCAG 2.1 Success Criterion 1.4.11 (Non-Text Contrast), visual objects such as UI controls (buttons, form field borders, focus indicators) and meaningful graphics must maintain a minimum contrast ratio of at least 3.0:1 against adjacent colors.

Relative luminance is the perceived brightness of any color normalized from 0 (pure black) to 1 (pure white). It accounts for human eye sensitivity, which perceives green as significantly brighter than red or blue.

Color blindness (such as Deuteranopia or Protanopia) reduces the ability to distinguish red and green hues. Contrast checkers evaluate light-to-dark luminance difference rather than color hue, ensuring text remains readable regardless of color vision deficiency.

In many jurisdictions, yes. In the US, Title III of the Americans with Disabilities Act (ADA) and Section 508 require accessible digital experiences. In Europe, the European Accessibility Act (EAA) mandates WCAG 2.1 AA compliance for commercial websites and mobile apps.

If your brand color fails contrast testing against white backgrounds, you can slightly lower its lightness (darken the text color) or darken the background color until it passes 4.5:1, without altering the core color hue.