1. What is Contrast Ratio?

The contrast ratio measures the difference in luminance between two colors. It's a dimensionless value ranging from 1:1 (no contrast) to 21:1 (maximum contrast between black and white).

2. How Does the Calculator Work?

The calculator uses the WCAG contrast ratio formula:

Where:

• \( L_{\text{light}} \) — Relative luminance of the lighter color (0-1)
• \( L_{\text{dark}} \) — Relative luminance of the darker color (0-1)
• 0.05 — Constant to prevent division by zero

Explanation: The equation compares the relative brightness of two colors, with higher values indicating greater contrast.

3. Importance of Contrast Ratio

Details: Contrast ratio is crucial for accessibility, particularly for visually impaired users. WCAG recommends minimum contrast ratios for text readability (4.5:1 for normal text, 3:1 for large text).

4. Using the Calculator

Tips: Enter relative luminance values between 0 and 1 for both light and dark colors. The calculator will compute the contrast ratio between them.

5. Frequently Asked Questions (FAQ)

Q1: What is relative luminance?
A: Relative luminance is the brightness of a color normalized to 0 for darkest black and 1 for brightest white.

Q2: What are good contrast ratios?
A: For AA compliance: 4.5:1 for normal text, 3:1 for large text. For AAA: 7:1 for normal text, 4.5:1 for large text.

Q3: How do I get relative luminance values?
A: They can be calculated from RGB values using a standard formula that accounts for human perception of different color channels.

Q4: Why add 0.05 in the formula?
A: This offset prevents division by zero and accounts for ambient light in typical viewing conditions.

Q5: Can I use this for color combinations?
A: Yes, this works for any two colors where you know their relative luminance values.