Summary

This EPUB to audio planner turns a word count or page count into audio length, MP3 size, days to finish and per-chapter figures. Choose one of six heartheweb voices, from 122 to 172 words per minute, plus playback speed and bitrate. An 80,000-word book at 146 WPM runs 9 h 08 min and about 1.05 GB at 256 kbps. It estimates the job in your browser and does not convert files.

EPUB TO AUDIO // PLANNER

EPUB to audio: know the length and size first

Enter a word count or page count. Get the audio length, MP3 size, days to finish and per-chapter figures for six narration voices. Runs in your browser.

Run the estimate How the numbers work

EPUB to audio estimator

Set the book length, pick a voice, then read the results. Everything updates as you type.

Audio length at 1x-
Your listening time-
Full MP3 size-
Days to finish-
Per chapter-
Words in the book-

HOW IT WORKS

Three formulas, no guesswork

Length = words / pace

Audio length at 1x is the word count divided by the voice's words per minute. An 80,000-word novel at 146 WPM runs 548 minutes, or 9 h 08 min. Your listening time divides that by your playback speed.

Size = bitrate x time / 8

A constant-bitrate MP3 weighs bitrate times duration, divided by eight. At 256 kbps, that same novel is about 1.05 GB. At 64 kbps it drops to roughly 263 MB, which is still intelligible for spoken word.

Days = listening time / daily minutes

Listening time at your speed, divided by the minutes you give it each day, rounded up. 6 h 05 min at 45 minutes a day is 9 days. Chapters are treated as equal slices, so use the per-chapter card as an average.

Plan an EPUB listen in four moves

  1. 1

    Get the length

    Use a word counter on the book text, or the page count if that is all you have. Pages are converted at the words-per-page value you set.

  2. 2

    Pick a voice and speed

    A slow voice like Late Night at 122 WPM adds hours to a long book. The Anchor at 172 WPM removes them. Match the voice to the book, not the clock.

  3. 3

    Choose a bitrate

    Spoken word survives lower bitrates better than music. Check the full size against your phone storage before you queue ten books.

  4. 4

    Split by chapter

    Per-chapter figures show what one file looks like. A 20-chapter novel at 256 kbps is about 53 MB a chapter, easy to download on a commute.

NOW PLAYING

A book fits the commute once you see the number

Nine hours sounds like a wall. Split into 20 chapters at 1.5x, it is 18 minutes a chapter, one leg of a train ride. The estimate turns a vague pile of unread books into a queue you can actually finish, one chapter per trip.

Commuter on a train with headphones holding an e-reader
FIELD NOTES

What the estimate leaves out

Front matter and notes

A word count that includes copyright pages, indexes and footnotes overstates what a narrator reads. Trim those first if you want a tighter number.

Hands-free, screen-free

Long books suit the commute, the run and the dishes. They also suit readers for whom a screen is the constraint. A planned queue beats a pile of unopened files.

Articles are the short version

For single pieces, the URL to audio converter page runs the same math on one article. Books are the same job at 100 times the size.

Limits

This is a planner, not a converter. It does not parse EPUB files, and it cannot promise exact seconds. Pauses, abbreviations and numbers change real narration time.

Common questions about EPUB to audio

Does this tool convert my EPUB file?
No. It plans the job. You enter a word count or page count and it returns audio length, MP3 size, chapter size and days to finish. Nothing is uploaded and nothing leaves your browser. To hear actual narration, paste an article URL on heartheweb.
Where do the words-per-minute numbers come from?
From the pace listed for each heartheweb voice on the homepage: Narrator 146, News Anchor 172, Your Friend 158, Documentary UK 140, The Scholar 134, Late Night 122. Pick the voice you would actually use and the estimate follows it.
How do I find the word count of an EPUB?
Open the text in any word counter, or count a few typical pages and multiply. If you only know the page count, switch the unit to pages and set words per page. The default is 250, and you can change it.
Is the MP3 size an exact figure?
The formula is exact for constant-bitrate MP3: bitrate times duration, divided by 8. At 256 kbps that is 32 KB per second, or about 115 MB per hour of audio. Real files add a small amount for tags and headers.
Why is playback speed not part of the file size?
The file is rendered at the voice's normal pace. Speeding it up in your player shortens listening time but does not shrink the file. That is why the tool shows two durations: audio length at 1x and your listening time.
Will a real narration match the estimate?
Close, not identical. Footnotes, tables, image captions and front matter change what gets read aloud, and pauses at chapter breaks add seconds. Treat the number as a planning figure, then check one chapter.
Is the tool free and does it store my numbers?
It is free, needs no account and runs entirely in your browser. The only thing sent is an anonymous usage ping when you first touch the widget. The numbers you type stay on your device.
READY TO TRANSMIT

Hear a voice before you plan a book

Paste an article URL, pick one of 42 voices and get an MP3 or a private podcast feed. Three articles a day are free.

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