I see modern blog page has number of minutes of read shown besides the author name and date time stamp.

I want to apply it on my static web page (not using any framework or Wordpress, no, I mean creating my own static HTML + CSS page), how do I estimate it? Is there a standard like 200 chars = 1 min read, but does that include the time taken by reading to look at images / photos?

I think this is an amazing concept to estimate the number of minutes of read for a blog article.