WCAG 2.0 Level AA:

  • Contrast ratio of 4.5:1 for normal text, or
  • 3:1 for large text (18 pt or 14 pt bold)

WCAG 2.0 Level AAA:

  • Contrast ratio of 7:1 for normal text, or
  • 4.5:1 for large text

Example Color Contrast Checker

There are several free contrast checkers available. The one pictured below is Contrast Analyser from The Paciello Group.

Contrast Analyser dialog includes an option for entering (or selecting from a web page) foreground and background colors, then provides four Pass/Fail ratings based on all WCAG criteria