Question 1

What is WCAG AA colour contrast?

Accepted Answer

WCAG 2.1 Level AA requires a contrast ratio of at least 4.5:1 for normal text and 3:1 for large text (18pt or 14pt bold) or UI components like buttons and icons.

Question 2

What contrast ratio is needed for WCAG AAA?

Accepted Answer

WCAG 2.1 Level AAA requires at least 7:1 contrast for normal text and 4.5:1 for large text. AAA is the highest accessibility standard and is recommended for text on critical information pages.

Question 3

How is colour contrast ratio calculated?

Accepted Answer

Contrast ratio = (L1 + 0.05) / (L2 + 0.05), where L1 is the relative luminance of the lighter colour and L2 is of the darker. Relative luminance is calculated from the linear RGB values using the formula defined in the WCAG 2.1 specification.

Color Contrast Checker

Related Tools