Color Contrast Checker
Check color contrast ratio against WCAG AA and AAA accessibility standards. Enter values for instant results with step-by-step formulas.
Formula
Contrast Ratio = (L1 + 0.05) / (L2 + 0.05) where L = relative luminance
WCAG 2.1 requires 4.5:1 for normal text (AA) and 7:1 for enhanced (AAA). Large text (18pt+): 3:1 (AA) and 4.5:1 (AAA).
Frequently Asked Questions
How do I interpret the result?
Results are displayed with a label and unit to help you understand the output. Many calculators include a short explanation or classification below the result (for example, a BMI category or risk level). Refer to the worked examples section on this page for real-world context.
How accurate are the results from Color Contrast Checker?
All calculations use established mathematical formulas and are performed with high-precision arithmetic. Results are accurate to the precision shown. For critical decisions in finance, medicine, or engineering, always verify results with a qualified professional.
Does Color Contrast Checker work offline?
Once the page is loaded, the calculation logic runs entirely in your browser. If you have already opened the page, most calculators will continue to work even if your internet connection is lost, since no server requests are needed for computation.
Can I share or bookmark my calculation?
You can bookmark the calculator page in your browser. Many calculators also display a shareable result summary you can copy. The page URL stays the same so returning to it will bring you back to the same tool.
How do I get the most accurate result?
Enter values as precisely as possible using the correct units for each field. Check that you have selected the right unit (e.g. kilograms vs pounds, meters vs feet) before calculating. Rounding inputs early can reduce output precision.
Can I use Color Contrast Checker on a mobile device?
Yes. All calculators on NovaCalculator are fully responsive and work on smartphones, tablets, and desktops. The layout adapts automatically to your screen size.