Contrast Ratio Checker — WCAG, Free
Calculate contrast from the relative luminance of two sRGB colors and compare common text thresholds. Use it while selecting colors rather than as an automated audit of a whole page.
- Runs in your browser
- Nothing is uploaded
- No signup; device limits apply
Numbers stay on your device. Nothing is sent to a server.
How to use this tool
Enter opaque foreground and background HEX values. If transparency or a background image is involved, determine the final composited colors before evaluating the combination.
Results and examples
Black #000000 against white #ffffff gives 21:1. WCAG AA uses 4.5:1 for normal text and 3:1 for large text; a rounded display must not turn a value below the threshold into a pass.
Limitations
- The tool does not inspect actual font size, weight, or composited page colors.
- A passing color pair does not establish overall accessibility conformance.
Fields
| Field | Guidance and constraints |
|---|---|
| Foreground (#hex) | Check the unit and format displayed beside this field. |
| Background (#hex) | Check the unit and format displayed beside this field. |
Data handling
Processing stays in the current browser tab; the site does not upload tool input for the calculation itself.
Sources
Frequently asked questions
What is the contrast between black and white?
Black #000000 against white #ffffff gives 21:1. WCAG AA uses 4.5:1 for normal text and 3:1 for large text; a rounded display must not turn a value below the threshold into a pass.
Does passing this check finish an accessibility audit?
The tool does not inspect actual font size, weight, or composited page colors. A passing color pair does not establish overall accessibility conformance.
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