Playback Speed Calculator
How long is a video, lecture, podcast or audiobook at 1.25×, 1.5× or 2× speed? Get the new duration and the time saved, with a table for every common playback speed.
How it works
New duration = original length ÷ playback speed · time saved = original − new duration · share saved = 1 − 1 ÷ speed
Playing media at a speed multiplier divides its running time by that number: at 2× a lecture takes half as long, at 1.5× two thirds as long. The saving grows more slowly than the speed — going from 1.5× to 2× saves only another 17% of the original time. Studies of sped-up lecture videos (e.g. Murphy et al., 2022) found comprehension holds up well to about 2× for most learners, though harder material benefits from slower speeds and rewatching.
Worked example
A 1:30:00 lecture at 1.5× takes 90 ÷ 1.5 = 60 minutes, so 1:00:00, saving 0:30:00 (33.33% of the time). At 2× it would take 0:45:00.
Sources: Murphy et al. (2022), Learning in double time, Applied Cognitive Psychology
Frequently asked questions
How long is a 1-hour video at 1.5× speed?
60 ÷ 1.5 = 40 minutes, saving 20 minutes. At 1.25× it takes 48 minutes and at 2× 30 minutes.
How do I calculate time at 2× speed?
Divide the length by 2. A 10-hour audiobook takes 5 hours at 2×, and 6 hours 40 minutes at 1.5×.
Does watching lectures at 2× hurt learning?
Research on recorded lectures found little loss of comprehension up to about 2× for many students, especially if they rewatch; above 2.5× comprehension drops. Difficult or unfamiliar topics are better at lower speeds.
What does 0.75× speed do?
It slows playback, so the content takes longer: a 40-minute video at 0.75× takes 53 minutes 20 seconds. That helps with language learning or dense material.
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This calculator is for educational purposes. Double-check important results before acting on them.