Color Contrast Analyzer
Accessibility is an important part of web design. By choosing the right colors, you can ensure that all visitors to your site can read your content.
The Color Contrast Analyzer will calculate the visibility based on the Web Content Accessibility Guidelines as recommended by the w3. There are two versions of the guidelines, version 1.0 which was presented in 1999, and Version 2.0 which is still a working draft.
The w3 recommendations define three levels of conformance to their guidelines. Priority 1, 2 and 3. Their 2.0 color contrast algorithms utilizes two of these-- Priority 2 (AA), and Priority 3 (AAA). Whether or not you need to reach an AAA conformance depends on your target audience. Read more about this on the w3 site. For large text (over 18 points) the contrast ratio for AA is 3:1 and for AAA 5:1. For small text it's 5:1 for AA and 7:1 for AAA.