ColorContrast
✦ 🎨 WCAG 2.1 AA (4.5:1) & AAA (7:1) · Relative Luminance Formulas

Verify Color Contrast, Accessible for Every Eye.

Free color calculators: WCAG 2.x contrast ratio checker with AA/AAA verdicts, and hex to RGB to HSL conversion with luminance. No sign-up.

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WCAG AA 4.5:1 Standard

Requires a minimum 4.5:1 contrast ratio for normal body text and 3:1 for large 18pt+ headings.

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Relative Luminance (L1/L2)

Formula weights green channel (0.7152) heaviest to match human optical retinal photopic sensitivity.

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Colorblind Simulation

Test palettes against protanopia, deuteranopia, and tritanopia color vision deficiencies.

Precision Tools

ColorContrast Calculators

📏 Hardware Tool

WCAG Contrast Checker

Contrast ratio from two hex colors — AA, AAA, and large-text verdicts per WCAG 2.x.

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🎨 Hardware Tool

Hex ↔ RGB ↔ HSL Converter

Convert any 6-digit hex to RGB and HSL — with relative luminance for palette work.

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Engineering Library

Technical Reference Guides

Engineering Guide

Relative Luminance: The Number That Decides Every Contrast Ratio

Green counts 3× more than red, sRGB needs linearizing, and vivid colors fail against each other — the math behind "readable."

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Engineering Guide

HSL for Palette Building: Stop Picking Colors, Start Deriving Them

Hue rotation, saturation families, and lightness targeting — the coordinate system that turns palettes into arithmetic.

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