Quick answer
Divide the original duration by playback speed. At twice the speed a recording takes half the time. At a speed below 1× it takes longer.
Step by step
- Convert the original runtime to seconds.
- Divide by the positive speed factor, such as 1.25 or 1.5. If different segments play at different speeds, calculate each separately.
- Convert the result back to minutes and seconds. For a schedule, add any pause or break time after the speed calculation.
Worked examples
Faster playback
A 90-minute recording at 1.5× takes 90 ÷ 1.5 = 60 minutes.
Slower playback
A 12:00 clip at 0.75× takes 720 ÷ 0.75 = 960 seconds, or 16:00.
Two speeds
Ten original minutes at 2× plus ten at 1× takes 5 + 10 = 15 minutes. For fractional seconds, add the exact segment times before rounding.
What to check
If you are editing chapter timestamps, use the speed-adjusted duration of each preceding segment. The total assumes uninterrupted playback until you add pauses.
Related guides
Sources
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