Is 18px considered large text for color contrast requirements?

Summary

Large text definitions depend on pt (points), not px. Misusing units can lead to incorrect contrast requirements.

Environment / Applicability

• Product / Feature: Siteimprove Platform
• Version / Platform: Applies to the current Siteimprove platform across all supported browsers and environments.
• Audience: Content authors, Web developers, Designers, Accessibility specialists, Digital governance and compliance teams
• Geographic / Language considerations: N/A

Question

Is 18 px considered large text for color contrast requirements?

Answer

• Verify your font size and unit:
  • If text is 18 px (or 19–20 px) and not bold, it is not large text
• Apply correct contrast thresholds:
  • 4.5:1 for normal text (AA)
  • 7.0:1 for normal text (AAA)
• Easiest fix:
  • Increase font size to 18 pt (24 px) or larger

Additional Details

Color contrast rules allow lower contrast for large text, so correctly defining “large” is important.

• For non-bold text:
  • Large text is 18 pt or larger
  • 18 pt = 24 px
• For bold text:
  • Large text is 14 pt or larger
  • 14 pt = 18.66 px

“Pt” (points) and “px” (CSS pixels) are different units. They are both valid in CSS but produce different sizes, similar to inches vs centimeters.

A common mistake occurs when someone reads “18 point” and focuses only on “18,” then sets the font size to 18 px, which equals 13.5 pt — smaller than required.