I've been using an app called Contrast for a while now, it's really convenient.

https://usecontrast.com/

If anyone ends up using it, be sure to check the support page, there are some useful power tips

https://usecontrast.com/support

Here's the objective criteria that W3C recommends for measuring it: https://www.w3.org/TR/WCAG20-TECHS/G18.html#G18-procedure

This is a good tool: https://webaim.org/resources/contrastchecker/

4.5:1 is considered good for body text.

The Google Chrome color picker for `color` CSS rules also displays the contrast ratio of the text in relation with the background color.