Color Contrast Checker Online
Calculate color contrast ratios and verify WCAG 2.1 AA & AAA accessibility compliance.
Input Parameters
Live Result
Details
Quick Answer & Understanding Your Result
A Color Contrast Checker calculates the relative luminance contrast ratio between foreground text and background colors (L1 / L2) to verify accessibility compliance against W3C WCAG 2.1 Level AA and AAA guidelines.
W3C WCAG 2.1 Contrast Standards
- Level AA (Regular Text < 18pt): Requires a minimum contrast ratio of 4.5:1.
- Level AA (Large Text >= 18pt / 14pt bold): Requires a minimum contrast ratio of 3.0:1.
- Level AAA (Enhanced / High Contrast): Requires 7.0:1 for regular text and 4.5:1 for large text.
- UI Components & Graphical Objects: Requires a minimum contrast ratio of 3.0:1.
Mathematical Contrast Formula
Contrast Ratio = (L1 + 0.05) / (L2 + 0.05) Where L1 is the relative luminance of the lighter color and L2 is the relative luminance of the darker color (0 <= L <= 1).
Pick your text and background colors above to inspect live contrast scores and WCAG compliance badges.
Formula & Calculation Logic
Mathematical FormulaWhere R_lin, G_lin, B_lin represent sRGB values linearized via gamma correction.
Step-by-Step Guide
Choose Foreground Color
Select or input HEX/RGB for text color.
Choose Background Color
Select or input HEX/RGB for background color.
Review Compliance Score
Inspect calculated ratio (e.g. 7.2:1) and AA/AAA Pass/Fail status.
Worked Examples Table
| Example | Input Values | Calculated Result | Explanation |
|---|---|---|---|
| Black Text (#000000) on White Background (#FFFFFF) | Maximum possible contrast ratio, passes all WCAG AA and AAA thresholds. | ||
| Dark Mode Neon Sky (#38BDF8 on #0F172A, 9.4:1) | Provides instant quantitative evaluation for comparative practical analysis. |
Frequently Asked Questions
Evidence-Based Methodology & Authoritative References
W3C Web Content Accessibility Guidelines (WCAG) 2.1
Standard: ISO / W3C / IETF Authoritative Domain Standard
Formula: L = 0.2126 × R_lin + 0.7152 × G_lin + 0.0722 × B_lin
Last Reviewed: August 21, 2026
Primary Source: W3C Web Content Accessibility Guidelines (WCAG) 2.1
Reference Document: Domain Standards & Specifications
Computation Privacy: 100% client-side 0ms computation, zero data retention
Calculated results are modeled based on standard scientific and mathematical formulas. Please verify with domain-specific technical documentation for specialized applications.
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Calculated results are modeled based on standard scientific and mathematical formulas. Please verify with domain-specific technical documentation for specialized applications.