How this calculator works
Playback speed divides the narrated length. At 1.5 times speed, ten narrated hours take 6 hours and 40 minutes, and the time saved is one third of the narration. Speeding up does not skip words, but it does compress pauses and speech; most listeners find 1.25 to 1.75 comfortable, and comprehension usually falls before the audio becomes unintelligible. The table shows the same book at the speeds most apps offer so you can pick a pace rather than guess.
Formula
listening time = narrated length / playback speed. time saved = narrated length - listening time. share saved = 1 - 1 / speed. speed needed = narrated length / available listening time.
Worked example
A 10-hour audiobook at 1.5 times speed takes 10 / 1.5 = 6.67 hours, which is 6 hours 40 minutes, and saves 3 hours 20 minutes, or 33.3 percent. To finish the same book in 7 hours you need a speed of 10 / 7 = 1.43.
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Frequently asked questions
Does a faster speed really save that much time?
Yes, in direct proportion. Two times speed halves the listening time, and 1.25 times saves 20 percent. The saving is exactly the narrated length times (1 - 1 / speed).
Is listening faster bad for comprehension?
It depends on the material and the listener. Easy fiction and familiar topics tolerate higher speeds than dense technical text. Try a short sample at the intended speed and check that you can still follow it before committing to a whole book.
Why does the app show a slightly different time?
Apps round to the nearest minute and some insert silence or chapter breaks that are not compressed. A difference of a minute or two is normal; the formula still gives the useful figure.
Can I use this for podcasts and lectures?
Yes. Any recording with a stated duration behaves the same way. The only caution is that music and recordings with heavy sound design may sound unnatural at high speeds.