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Color Contrast Checker

Check the WCAG contrast ratio between two colors, with AA and AAA results for normal and large text.

Almost before we knew it, we had left the ground.
15.96:1

contrast ratio

  • PassAA normal
  • PassAA large
  • PassAAA normal
  • PassAAA large

How to use it

  1. Pick the text color Use the swatch or type a hex value.
  2. Pick the background The colour behind the text.
  3. Read the ratio See the ratio and WCAG pass/fail results.

Examples

black on white 21:1
AA normal needs 4.5:1

About this tool

Readable text needs enough contrast against its background, and accessibility guidelines put real numbers on it. This checker measures the WCAG contrast ratio between any two colours and shows whether the pair passes AA and AAA for both normal and large text.

A live preview lets you see the combination as you tune it, so you can find a pair that’s both on-brand and accessible. The ratio uses the official WCAG 2.1 luminance formula, and everything is calculated in your browser.

Frequently asked questions

What contrast ratio do I need?

WCAG AA needs 4.5:1 for normal text and 3:1 for large text; AAA needs 7:1 and 4.5:1. Large text is roughly 18pt, or 14pt bold.

How is the ratio calculated?

From the relative luminance of each colour, following the WCAG 2.1 formula, giving a value between 1:1 and 21:1.

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Updated June 13, 2026