A fast three-step workflow
How to use the color contrast checker
- 1
Enter the known information
Add only the values or source text the calculation needs. Useful examples and safe defaults are already selected.
- 2
Adjust the assumptions
Use the extra controls to match your real task instead of accepting a hidden one-size-fits-all assumption.
- 3
Review the complete result
Check the main answer, supporting values and method before copying, downloading or acting on the result.
What makes this tool more useful
Test two colors, preview real text and see which WCAG thresholds pass. Suggested alternatives keep one color fixed and adjust the other.
How the calculation works
Relative luminance is calculated from sRGB values and contrast ratio uses the WCAG formula (L1 + 0.05) / (L2 + 0.05).
Review buttons, links, body copy, badges or design-system color pairs.
Private, fast and mobile-ready
The workspace runs with browser JavaScript and does not submit entered values to a Rantey calculation endpoint. Controls use readable labels, large touch targets and responsive result panels for narrow screens.
Frequently asked questions
Color Contrast Checker FAQ
Is Color Contrast Checker free?+
Yes. The complete tool is free to use without registration, subscriptions or a watermark.
Does Color Contrast Checker work on mobile?+
Yes. Inputs, actions and result panels stack for current Android, iPhone, tablet and desktop browsers.
Is my information uploaded?+
No. Values and pasted text are processed in the current browser tab and are not sent to a Rantey application endpoint.
How should I use the result?+
Review the displayed assumptions, method and comparison details. The result is an estimate or transformation based on the values you entered.