This tool uses the WCAG 2 (the world's authority on web accessibility) formula for color contrast. For level AA compliance, your text should have a contrast ratio of 4.5:1 (don't worry, our tool will figure this out for you!). For level AAA compliance your text should have a contrast ration of 7:1-however, if your text is large (18+ point or 14 point if the text is bold), then your ratio can be 3:1 for AA compliance and 4.5:1 for AAA.