On the Origin of Species By Means of Natural Selection
10h 20mof reading at 250 wpm
On the Origin of Species By Means of Natural Selection by Darwin, Charles runs to 154,905 words — about 10h 20m of reading at an average adult pace of 250 words per minute, or roughly 563 pages at typical paperback density.
Extent 154,905 words · 7,231 distinct forms · 5,323 sentences · F–K grade 14.4
SOURCE·Project Gutenberg full texts·computed from the full text·REVIEWED JUL 2026
Above the rule one mark per reading hour at 250 wpmBelow a folio every 50 pages at 275 words to the page
SOURCE·Project Gutenberg full texts·counted from the text, not a publisher's page count·REVIEWED JUL 2026
How this is worked out
- The Project Gutenberg plain-text edition is fetched, then Gutenberg's header and licence footer are struck at the
*** START ***and*** END ***markers. Nothing is taken from a publisher's listing. - What remains is counted as that edition sets it: 154,905 words, 5,323 sentences, syllables by vowel-group heuristic.
- Words are divided by a stated reading rate. This page's headline uses 250 words a minute; a duration printed without its rate cannot be checked, so the rate travels with every figure and the table below runs 150–450 wpm.
- Minutes are rounded once, to the nearest minute, and set as h:mm. Nothing on this page is rounded twice.
- The page extent is a courtesy conversion at 275 words to the page — a typesetting figure, not a property of the book.
words ÷ rate = minutes 154,905 ÷ 250 wpm = 620 min → 10h 20m words ÷ density = extent 154,905 ÷ 275 w/pp = 563 pages
How long it takes to read, by reading speed
Most adults read prose at 200–300 words per minute. Reading speed varies far more between people than most reading-time estimates admit, so here is the whole range.
| Reading speed | Total time | At 30 min/day | At 1 hour/day |
|---|---|---|---|
| Slow / careful (150 wpm) | 17h 13m | 35 days | 18 days |
| Below average (200 wpm) | 12h 55m | 26 days | 13 days |
| Average adult (250 wpm) | 10h 20m | 21 days | 11 days |
| Fast (300 wpm) | 8h 36m | 18 days | 9 days |
| Very fast (450 wpm) | 5h 44m | 12 days | 6 days |
The full measurement
| Total words | 154,905 |
|---|---|
| Unique words | 7,231 |
| Lexical diversity | 4.67% unique words as a share of total |
| Sentences | 5,323 |
| Average sentence length | 29.1 words |
| Average syllables per word | 1.58 |
| Long words (3+ syllables) | 15.7% |
| Chapters detected | 28 — averaging 5,532 words |
| Flesch–Kincaid grade | 14.4 |
| Flesch reading ease | 43.7 higher is easier; 60–70 is plain English |
| Gunning fog index | 17.9 |
| Coleman–Liau index | 11.7 |
Computed from the Project Gutenberg plain-text edition with the Gutenberg header and licence footer removed. See how and why your count may differ.
SOURCE·Project Gutenberg full texts·ebook no. 1228·REVIEWED JUL 2026
Reading it in evenings
The same 154,905 words, divided by the habit rather than by the hour — and then a rate of your own, if 250 wpm is not yours.
SOURCE·Project Gutenberg full texts·reading rate stated: 250 wpm·REVIEWED JUL 2026
Average adult prose speed is 200–300 wpm. Not sure? Time yourself on one page.
Is it a hard read?
Four different readability formulas agree it is difficult — college level: Flesch–Kincaid puts it at grade 14.4, Gunning fog at 17.9, Coleman–Liau at 11.7. The Flesch reading-ease score of 43.7 is heavy going by modern standards.
The mechanics behind that: sentences average 29.1 words (modern prose tends to run 15–20), and 15.7% of words are three syllables or longer. Its vocabulary is fairly repetitive — 7,231 distinct words, or 4.67% of the total.
A caution about all of this: readability formulas measure sentence and word length, nothing more. They cannot see irony, dialect, allusion or an unreliable narrator. A book can score as "easy" and still be genuinely difficult to follow.
The second question
What people ask once the duration is on the table.
How many words are in On the Origin of Species By Means of Natural Selection?
154,905 words in the Project Gutenberg edition, made up of 7,231 distinct words across 5,323 sentences. That is longer than 75% of the books measured on this site.
How long does it take to read On the Origin of Species By Means of Natural Selection?
About 10h 20m at an average adult reading speed of 250 words per minute. A slower reader at 150 wpm would need roughly 17h 13m; a fast reader at 400 wpm about 6h 27m.
What reading level is On the Origin of Species By Means of Natural Selection?
It scores 14.4 on the Flesch–Kincaid grade scale — difficult — college level. Its Flesch reading-ease score is 43.7, sentences average 29.1 words, and 15.7% of its words run to three syllables or more.
How many pages is On the Origin of Species By Means of Natural Selection?
Page counts depend entirely on the edition — font, trim size and margins all change them, which is why this site measures words instead. At a typical trade-paperback density of about 275 words per page, 154,905 words works out to roughly 563 pages.
The rest of Darwin, Charles’s shelf, measured
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Nearest neighbours by word count — the same evening, a different book.
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Measured from the Project Gutenberg plain-text edition, ebook no. 1228, with Gutenberg’s header and licence footer struck before counting. 154,905 words, 5,323 sentences, 7,231 distinct forms. No text of the work is set anywhere on this site — only measurements of it.
The extent of 563 pages is a conversion at 275 words to the page, not this edition’s foliation: a page count belongs to a typesetting, never to a book. Reading time assumes 250 words a minute and is stated with its rate everywhere it appears.
SOURCE·Project Gutenberg ebook no. 1228·US public domain·REVIEWED JUL 2026
Word counts and reading levels are computed from a specific public-domain edition and will differ from other editions and from other counting methods — see the method page.
