Colour Contrast Checker
A free, browser-based converter. Runs entirely in your browser — no sign up, nothing stored.
100% FreeRuns in your browserBasic
Contrast checker
Sample text — The quick brown fox
4.98:1
contrast ratio
AA normal ✓AA large ✓AAA normal ✗AAA large ✓
WCAG 2.1 contrast. AA needs 4.5:1 (3:1 large text); AAA needs 7:1 (4.5:1 large). Guidance only.
How to use this calculator
- Choose a text colour and a background colour.
- Read the contrast ratio and which WCAG levels pass.
How it works
Uses the WCAG 2.1 relative-luminance formula. AA needs 4.5:1 (3:1 for large text); AAA needs 7:1 (4.5:1 large).
Worked example
Black on white. = 21:1 — passes every level.
Tips
- Runs entirely in your browser. Your input is not uploaded or stored.
Frequently asked questions
What counts as large text?
About 18.66px bold or 24px regular and up.
Is this official?
It implements the WCAG maths, but always test real designs too.
Related tools
Tip: Enter any known values to calculate the remaining results.
All calculations run in your browser. Your inputs are never saved or transmitted.