What counts as large text under WCAG?

WCAG defines large text as at least 18pt (24px) regular, or at least 14pt bold (about 18.66px at 700 weight). At those sizes the relaxed thresholds apply.

What contrast ratio does large text need?

Large text needs at least 3:1 for AA and 4.5:1 for AAA. That is lower than normal text, which needs 4.5:1 for AA and 7:1 for AAA, because larger glyphs are easier to read at lower contrast.

Why does my heading fail when I think it should pass?

If the font size you entered is below 24px (or below 18.66px when bold), the tool applies the stricter normal-text thresholds. Increase the size, make it bold, or pick a darker colour.

Does bold really change the rule?

Yes. 14pt bold (roughly 18.66px at 700 weight) qualifies as large text even though 14pt regular does not. Bold strokes are thicker, so WCAG allows the relaxed threshold at a smaller size.

Is anything sent to a server?

No. All luminance and contrast maths runs locally in your browser, and the preview is rendered client-side. Nothing about your colours or text is transmitted.

Large Text Contrast Checker

Headings, hero copy, and call-to-action buttons are usually large text, and WCAG deliberately holds large text to a lower contrast bar than body copy. Many teams over-tighten their palette because they apply the 4.5:1 body-text rule to everything. This checker applies the correct relaxed thresholds so you can use a lighter brand colour on a heading without failing accessibility.

How it works

The tool computes the WCAG contrast ratio between two colours and then chooses thresholds based on whether the text qualifies as large:

Each colour is converted to relative luminance using the linearised sRGB formula 0.2126*R + 0.7152*G + 0.0722*B.
The contrast ratio is (Llighter + 0.05) / (Ldarker + 0.05).
Text qualifies as large when it is at least 24px regular, or at least 18.66px bold (14pt at 700 weight).
For large text, AA requires 3:1 and AAA requires 4.5:1. For normal text the stricter 4.5:1 and 7:1 apply.

The live preview renders your actual colours at the size and weight you entered, so you can confirm the numeric verdict visually.

Example and notes

A muted slate #5b6472 on white is 4.43:1 — that fails AA for body text but passes AA for a 24px heading.
The 14pt-bold exemption is easy to miss: 14pt bold is large, but 14pt regular is not. Always tick the Bold box only when the real weight is 700+.
Point-to-pixel conversion assumes the common 96 DPI / 1pt = 1.333px baseline (18pt ≈ 24px, 14pt ≈ 18.66px). If your design uses a different root size, judge by the rendered pixel size.
Meeting large-text contrast covers the contrast criterion only — it does not exempt you from minimum touch-target size, focus indicators, or other WCAG success criteria.