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Audiobook Playback Duration & Time Difference

Calculate listening duration at an entered playback speed, including time saved above 1× or extra time below 1×.

Formula & worked example
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Calculator inputs

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How to use this calculator

Enter the known values in the units shown. Results update as you type.
Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
Use the worked example to check the method. Reset restores the starting fields.

Private by default

Inputs and results stay in this browser tab. Bookify does not upload or store the values you enter.

Formula and method

A 12-hour audiobook played at 1.5× takes eight hours, saving four hours. At 0.5× it takes 24 hours, adding 12 hours.

Listening duration = original duration ÷ speed multiplier; time saved = original duration − listening duration

Worked example

Enter these known values and leave the other values blank.

Original duration at 1×: 12:0 hrs / min
Playback speed multiplier: 1.5

Listening duration: 8:0 hrs / min
Time saved compared with 1×: 4:0 hrs / min

Assumptions and limitations

Original duration and playback multiplier are positive. A multiplier of 1 means normal speed.
Hours-and-minutes entries use a colon, such as 12:30 for 12 hours 30 minutes. Other retained duration units are selectable.
Speed stays constant for the entire recording. The model does not assess comprehension or listening comfort.

Common questions

What happens below normal playback speed?

The listening duration becomes longer than the original. The result shows extra time instead of time saved.

Can I calculate the speed needed for a target duration?

Yes. Unlock and clear the speed field, then enter original and target listening durations. The required multiplier is their ratio.

References

The calculation equations, inverse formulas, units, and input rules were imported from this source. Bookify provides the interface and equation solver.

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