Here is the four text with different level of grey:

enter image description here

As you can see, the first line is very difficult to read, and the last one is the best to read. So, is there any science number behind this contrast and readability? What is the contrast that the human eyes can read easily? Which one is hard? Of course, you can find someone to do testing. But, any proved number had been proof? Thanks.


2 Answers 2


As Web Content Accessibility Guidelines (WCAG2.0) claimed

level AA requires a contrast ratio of 4.5:1 for normal text and 3:1 for large text.

Level AAA requires a contrast ratio of 7:1 for normal text and 4.5:1 for large text.

You can use contract color checker at WebAIM


The Guidelines have been specified by the user below.

A tool I like using is the Colour Contrast Analyser. A desktop application that allows you to eye drop any color on your screen and outputs the contrast ratio.

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