AA Level (minimum): normal text β₯ 4.5:1, large text (β₯18pt or β₯14pt bold) β₯ 3:1
AAA Level (enhanced): normal text β₯ 7:1, large text β₯ 4.5:1
Contrast ratios range from 1:1 (identical) to 21:1 (black on white).
Color contrast measures the difference in luminance between foreground (text) and background colors, expressed as a ratio (e.g., 4.5:1). Higher ratios mean easier readability. Low contrast causes reading difficulties for visually impaired users, older adults, and anyone using devices in bright light.
Government websites, public services, e-commerce, educational platforms typically require AA compliance. Many countries mandate WCAG 2.1 AA for public-facing websites. AAA is a higher standard to aim for when possible.
To improve contrast: 1) Use darker text (closer to #000); 2) Use lighter backgrounds (closer to #FFF); 3) Avoid light gray on white or dark gray on black; 4) Test adjusted combinations with this tool.
Large text (β₯18pt or β₯14pt bold) is inherently easier to read, so it has lower contrast requirements. Small text needs higher contrast to remain legible. This is based on vision science research used in WCAG guidelines.
This tool uses the WCAG 2.1 relative luminance algorithm based on the sRGB color space. It accounts for human perception differences (e.g., higher sensitivity to green), making it the internationally recognized standard.
Yes. After loading, all calculations work offline since everything runs in your browser.