WCAG Contrast, Explained Without the Jargon

The ratio

Contrast ratio is a number between 1:1 (no contrast - invisible) and 21:1 (pure black on pure white). It compares the relative luminance of two colors.

The thresholds

3:1 - minimum for large text (18pt+ or 14pt bold) and graphical elements (AA Large).

4.5:1 - minimum for body text (AA).

7:1 - enhanced contrast (AAA).

What about APCA?

The Accessible Perceptual Contrast Algorithm, used in WCAG 3 drafts, models how humans actually perceive contrast against different backgrounds. It is more accurate but not yet a hard requirement.

Test your colors instantly in the Contrast Checker.