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Contrast Ratio Calculator

Find the WCAG contrast ratio between two luminances.

Calculated Output

Contrast ratio (:1) 4.2

Formula: ratio = (Lmax + 0.05) / (Lmin + 0.05)

Step-by-Step Breakdown

1. Values used:

2. Luminance 1 (0-1) = 1

3. Luminance 2 (0-1) = 0.2

5. Contrast ratio = 4.2:1

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The math behind it

ratio = (lighter + 0.05) / (darker + 0.05) using relative luminance. WCAG wants 4.5:1 for normal text.

Luminances 1 and 0.2 give a 4.2:1 ratio.

What ratio passes WCAG AA?

4.5:1 for normal text, 3:1 for large text.