How the time is worked out
Time is the word count divided by the speed: 1,000 words at 220 words per minute is 4.55 minutes, which is 4 minutes 33 seconds once the fraction of a minute is turned into seconds and rounded to the nearest second. The same 1,000 words spoken at 130 words per minute take 7 minutes 42 seconds.
Pasted text is counted with the same method as the word counter — the browser's Unicode word segmentation — and the default speeds are the same 220 and 130 words per minute, so the two tools agree.
Choosing a speed
Reading speed varies a great deal by person and material. A 2019 review of reading-rate studies by Marc Brysbaert put the average for adults reading English silently at about 238 words a minute for non-fiction and 260 for fiction, and dense technical text is read more slowly. 220 is a deliberately cautious default for estimating how long an article will take.
Speaking is slower. Many presenters speak at roughly 120 to 160 words a minute, and slow down further for an audience hearing unfamiliar material, with pauses, slides or questions. To time a speech, read a page aloud against a clock, divide the words by the minutes, and put your own figure in the speaking box.