How to Calculate WCAG Color Contrast Checker

What is WCAG Color Contrast Checker?

WCAG contrast requirements ensure text and UI elements are readable for people with low vision. AA standard requires 4.5:1 for normal text and 3:1 for large text.

Formula

Contrast ratio = (L1+0.05)/(L2+0.05) where L = relative luminance

L: Relative luminance (0-1)
R,G,B: Linearised RGB components (0-1)

Step-by-Step Guide

1Relative luminance = 0.2126R + 0.7152G + 0.0722B (linearised RGB)
2Contrast ratio = (L_lighter + 0.05) / (L_darker + 0.05)
3AA: 4.5:1 normal text, 3:1 large text; AAA: 7:1 normal text

Worked Examples

Input

Dark grey #333333 on white #FFFFFF

Result

Contrast ratio approx 12.6:1 - passes WCAG AAA

Frequently Asked Questions

What is Color Contrast Wcag?

WCAG contrast requirements ensure text and UI elements are readable for people with low vision. AA standard requires 4

How accurate is the Color Contrast Wcag calculator?

The calculator uses the standard published formula for color contrast wcag. Results are accurate to the precision of the inputs you provide. For financial, medical, or legal decisions, always verify with a qualified professional.

What units does the Color Contrast Wcag calculator use?

This calculator works with inches, watts. You can enter values in the units shown — the calculator handles all conversions internally.

What formula does the Color Contrast Wcag calculator use?

The core formula is: Relative luminance = 0.2126R + 0.7152G + 0.0722B (linearised RGB). Each step in the calculation is shown so you can verify the result manually.

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