Contrast Ratio Checker
Get the contrast ratio between two colours as a precise number.
The ratio itself
The contrast between two colours is expressed as a ratio, from 1:1 for identical colours up to 21:1 for black on white. This calculates that ratio for any two colours, giving you the precise number to check against accessibility requirements or compare combinations.
Enter two colours to see their contrast ratio.
Reading the number
The ratio is what accessibility standards are defined against: a common requirement is at least 4.5 to 1 for normal text and 3 to 1 for large text, with stricter targets for enhanced accessibility. Knowing the raw number lets you check any pair against those thresholds and compare candidates directly — a combination at 7 to 1 is comfortably readable, one at 2 to 1 is not. Because contrast is measured against how the eye perceives lightness rather than a simple difference in the colour values, it is not something you can reliably judge by eye, which is exactly why the calculated ratio matters. It is the objective figure behind readable, accessible colour choices.
Common questions
What contrast ratio counts as readable?
A common requirement is at least 4.5 to 1 for normal text and 3 to 1 for large text, with stricter targets for enhanced accessibility.
Why not just judge contrast by eye?
Because it is measured against how the eye perceives lightness, not a simple colour difference, so text that looks fine can fail. The number is objective.
Is anything uploaded?
No. The calculation happens in your browser.