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Calculate the estimated reading time of an article using JavaScript

michaelburrows profile image Michael Burrows Originally published at w3collective.com ・1 min read

You’ve probably seen displayed on websites like Medium an estimated reading time. This metric helps users decide if they read the article immediately, or save it for later. In this tutorial we’ll be using JavaScript to calculate the estimated reading time of an article.

First in a HTML document let’s create a dummy article as follows:

<article id="article">
  <h1>Lorem ipsum dolor sit amet</h1>
  <p>
    Minus ullam est commodi facere repudiandae sit. Ab quibusdam totam
    veniam ducimus ut consequatur sit. Ea et nulla quaerat. Et temporibus
    quas numquam quas dolor vero accusantium numquam.
  </p>
  <!-- repeat <p> tag several times here -->
</article>
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Then where you would like the reading time to be displayed in the page add this:

<p><span id="time"></span> minute read</p>
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Now for the JavaScript functionality to calculate the reading time:

function readingTime() {
  const text = document.getElementById("article").innerText;
  const wpm = 225;
  const words = text.trim().split(/\s+/).length;
  const time = Math.ceil(words / wpm);
  document.getElementById("time").innerText = time;
}
readingTime();
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Here’s a breakdown of what the readingTime() function is doing:

  • text – fetch the article text so we can preform the calculations.
  • wpm – average adult reading speed (words per minute).
  • words – calculate total number of words (length) by splitting at each whitespace.
  • time – calculates the read time rounded up to the nearest whole number.

With the time calculated we then output the number into <span id="time"></span>.

That concludes this tutorial, you now know how to display the estimated reading time for an article that can easily be dropped into a blog or news website.

Discussion (3)

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daviddalbusco profile image
David Dal Busco

Interesting share @michaelburrows .xyz 👍

The constant value 225 for wpm is a known general accepted value or what's its source?

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singhnikhurpa profile image
Bhupesh Singh Nikhurpa

According to a speed-reading test sponsored by Staples as part of an e-book promotion, here are the typical speeds at which humans read, and in theory comprehend, at various stages of educational development :

Third-grade students = 150 words per minute (wpm)
Eighth grade students = 250 wpm
Average college student = 450 wpm
Average "high-level exec" = 575 wpm
Average college professor = 675 wpm
Speed readers = 1,500 wpm
World speed reading champion = 4,700 wpm
Average adult = 300 wpm

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daviddalbusco profile image
David Dal Busco

Excellent! Thanks for the metrics 👍.

Proven numbers and code snippets, it seems that I have no more excuses to not add such information to our dashboard 😉.