How Long Will Your Audiobook Be? Word Count → Listening Minutes

The 90,000-word question

You finished a draft. It clocks in at 92,341 words. Your editor wants to know how long the audiobook will run so they can quote a narrator. Audible's pricing tiers care, ACX's royalty splits care, your launch plan cares.

The honest answer takes one line of arithmetic. The reason most authors don't have it ready is that no writing tool shows it. Scrivener counts words. Word counts words. Google Docs counts words. None of them tell you that 92,341 words equals roughly ten hours and fifteen minutes of audio at a comfortable narration pace. That's the gap we wanted closed.

The formula

Two numbers do all the work:

240 words per minute — average silent reading speed for an adult reading prose for pleasure. (Faster for genre fiction, slower for technical or literary, but 240 is the steady middle.)
150 words per minute — natural narration pace for an audiobook. Slow enough for diction and breath, fast enough not to drag.

That gives you the two readouts you actually want:

audio_minutes = words / 150
silent_read_minutes = words / 240

Memorize 150 and the rest falls out. A chapter that takes you ten minutes to read silently will take roughly sixteen minutes to listen to. A short story of 5,000 words is half an hour of audio. A 50,000-word NaNoWriMo draft is five and a half hours.

Where 150 wpm comes from

The number isn't arbitrary. Professional audiobook narrators target about 9,300 finished words per hour — ACX's published standard, which works out to roughly 155 wpm. We round down to 150 on purpose: real narration has pauses (between paragraphs, chapters, dramatic beats), AI narration adds structural pauses 155 wpm doesn't account for, and conservative estimates under-promise. An author who plans for ten hours and ships nine and a half disappoints no one. The reverse breaks marketing copy.

So when MimicReader's editor says "8m audio" next to your 1,200-word chapter, that's 1200 / 150 = 8 minutes — and it'll come out almost exactly that long when you generate.

        The conservative bias is on purpose. 150 wpm sits a hair below ACX's 9,300 words/hour. The penalty is being five minutes early on a six-hour book. The reward is never pitching a four-hour audiobook that turns into three.
    

Reference table — what your manuscript will sound like

Word count	Silent read	Audiobook runtime	What that is
5,000	~21 min	~33 min	Short story / single chapter
10,000	~42 min	~1 hr 7 min	Novelette
20,000	~83 min	~2 hr 13 min	Short novella
30,000	~2 hr 5 min	~3 hr 20 min	Standard novella
50,000	~3 hr 28 min	~5 hr 33 min	NaNoWriMo target / short novel
70,000	~4 hr 51 min	~7 hr 47 min	YA novel / commercial fiction
80,000	~5 hr 33 min	~8 hr 53 min	Typical adult novel
100,000	~6 hr 56 min	~11 hr 7 min	Long literary / fantasy novel
150,000	~10 hr 25 min	~16 hr 40 min	Epic / doorstop fantasy
200,000	~13 hr 53 min	~22 hr 13 min	Anna Karenina territory

Print this if you write longhand. The middle rows are where most indie titles land — and where the runtime decisions get made.

Why this number matters for indie authors

Audible pricing tiers

Audible groups audiobooks into runtime buckets that quietly drive what listeners expect to pay:

Under 1 hour — short story / sample. Often $0.99-$1.99.
1-3 hours — novelette. Single credit, priced low ($3-6).
3-5 hours — standard novella, the "lunch hour" length. $7-10.
5-10 hours — most novels live here. $14-25, the sweet spot for member credits.
10-20 hours — long novels and short non-fiction. Premium $20-30 range.
20+ hours — epic fantasy, doorstop biographies. $30+, often two credits.

If you're sitting at 78,000 words you'll land at the top of the 5-10 hour bracket. Trim to 65,000 and you're solidly in it with breathing room — but you'll also lose 10% of your retail price ceiling. That's a runtime-driven business decision, and you need the number to make it.

Recording budget

Hiring a narrator? Industry rate is $200-$400 per finished hour (PFH) for a working pro, $100-200 for newcomers, $500+ for SAG-AFTRA names. Multiply by runtime, not word count. Your 80,000-word novel at $300 PFH is $2,670 — not a number you want to discover after signing. Knowing the runtime before you pitch lets you set a royalty-share offer that pencils out, budget cash up front, or decide that AI narration is the realistic path. (At MimicReader 1 credit per hour, the same 80,000-word novel narrates for £9 in Standard or £14 in Premium.)

Chapter targets

Listeners think in time: "How long is this chapter? Can I finish it before I get off the train?" Twenty to twenty-five minutes is the comfortable upper bound for a listening session. Reverse the math: 25 minutes × 150 wpm = 3,750 words per chapter. If you're consistently writing 6,000-word chapters that's a 40-minute audio block — fine for fantasy, a problem for thrillers. Knowing audio length per chapter as you draft lets you balance pacing in the medium people will actually consume it in.

How MimicReader shows you live

Open any project chapter in the Writing Studio. The editor header reads:

1,234 words · 5m read · 8m audio

That row updates as you type — debounced on save, so it doesn't flicker on every keystroke, but always current within a second or two. Pure JavaScript on the client, zero round-trips. Switch into composition mode (fullscreen, distraction-free) and the same readout appears in the floating status bar at the bottom of the screen.

The project sidebar shows a running total for the whole book. Targeting an 8-hour audiobook average? You'll see 7h 12m as you write chapter 18 and know you've got 48 minutes of audio left to fill — about 7,200 words, two medium chapters or one long one. Decisions you can make in the same window where you're already writing.

How this compares to ACX's calculator

ACX (Amazon's audiobook production marketplace) publishes a similar calculator, used by narrators to estimate jobs. Their standard is 9,300 finished words per hour — essentially 155 wpm. The MimicReader number of 150 wpm sits about 3% under that, giving a slightly conservative runtime estimate.

The difference at scale:

80,000-word novel: ACX says ~8h 36m, MimicReader says ~8h 53m
120,000-word novel: ACX says ~12h 54m, MimicReader says ~13h 20m

Both are correct — they're measuring the same thing with slightly different rounding. What you can't do with ACX's calculator is have it visible while you write. It's a separate tab, a separate intention. MimicReader's belief is that the runtime number is interesting while you're shaping the chapter, not afterward when you remember to check.

What other writing tools show

Scrivener, Word, Google Docs, Ulysses, iA Writer, Bear — all show word and character counts, none show audio time. This isn't a knock; those tools predate the indie audiobook boom by a decade. But it's the gap. If you write in MimicReader's Writing Studio, the runtime is always one glance away.

Write with audio runtime always visible

Free account includes Writing Studio with live word count, reading time, and audiobook runtime. 1 hour of audiobook generation per month, no credit card.

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Bottom line

Every author publishing in audio should know their runtime cold. It drives pricing, narrator budget, marketing copy, chapter structure, and listener expectation. The math is one division. The reason most authors guess is that no editor surfaces it. MimicReader does — in the chapter editor, composition mode, and project sidebar, updated live. words / 150 sounds trivial until you've shipped a book and realized you would've structured it differently if you'd been watching the number from page one.