WCAG contrast checker
WCAG 2.1 contrast ratio between a foreground and background color, with pass / fail for the standard accessibility thresholds.
Sample textThe quick brown fox jumps over the lazy dog.
Contrast ratio17.40:1
✓ AA LargeText 18pt+ or 14pt+ bold≥ 3.0:1
✓ AABody text under 18pt≥ 4.5:1
✓ AAA LargeLarge text, enhanced contrast≥ 4.5:1
✓ AAABody text, enhanced contrast≥ 7.0:1
What is a contrast ratio?
The WCAG 2.x contrast ratio measures the difference in relative luminance between two colors — essentially, how much brighter one is than the other when accounting for human perception of brightness across the RGB channels (green contributes most, blue least). Ratios range from 1:1 (identical) to 21:1 (pure black on pure white).
WCAG thresholds
- 3:1 (AA Large) — minimum for text 18pt and larger, or 14pt and larger when bold.
- 4.5:1 (AA) — minimum for normal body text under 18pt. The most commonly cited threshold.
- 7:1 (AAA) — enhanced contrast for normal body text. Aspirational; required only for government and high-accessibility contexts.
UI components and graphical objects (icons, form borders) require a minimum 3:1 ratio against adjacent colors per WCAG 2.1 SC 1.4.11.