Check WCAG 2.1 AA & AAA accessibility contrast ratios between any two colors — instantly.
The minimum legal and practical standard. Requires 4.5:1 for normal text and 3:1 for large text (18pt+) or bold large text (14pt bold+). Also requires 3:1 for non-text UI components such as buttons and form fields.
The enhanced accessibility standard. Requires 7:1 for normal text and 4.5:1 for large text. AAA compliance is not required for entire sites but is ideal for high-readability interfaces such as medical or government portals.
Luminance is the perceived brightness of a color on a scale of 0 (black) to 1 (white). The contrast ratio formula is (L1 + 0.05) / (L2 + 0.05) where L1 is the lighter luminance. Black-on-white achieves the maximum ratio of 21:1.
~300 million people worldwide have color vision deficiency; ~2.2 billion have some form of vision impairment. Adequate contrast benefits everyone — especially in bright sunlight, on low-quality screens, or for older users with reduced contrast sensitivity.