# Statistics on Harry Potter chapter length

I'm looking for some statistics on typical Harry Potter chapter word count.

A nicely graphed distribution would be nice, but I'll accept an answer that has something equivalent to the average, standard deviation, and quartiles.

• I'm mainly concerned with the series as whole, not each book separately. (But you can include that too if you want.)
– ibid
Jan 21 '19 at 12:22
• You may want to specify an edition as the word counts may vary, unless that's insignificant enough that you don't care about it.
– Alex
Jan 21 '19 at 21:15

To calculate this answer I used the text from the official Pottermore ePubs (each chapter is saved as a seperate html file). I ran the htmls through a utility I found to convert them to txt, and then used the unix `wc -w` command to generate a list of chapter word counts. (Feel free to play around with the data on your own.)

I plugged this into excel and did a few calculations.

Note: All the below data uses the UK text. The American text tends to be a bit shorter.

• The longest chapter is Book 5, Chapter 13 - "Detention with Dolores" at 9,001 words.
• Not counting the epilogue, the shortest chapter is Book 3, Chapter 20 - "The Dementors’ Kiss" at 2,018 words.
• The average chapter length is 5,547 words.
• The standard deviation is 1,525 words.
• 50% of the chapters are between 4,464 and 6,613 words. (i.e. the first and third quartile)

Here is how the distribution looks with a bin width of 500 words. However it's worth noting that some factors have a significant effect on chapter length, such as the length of the book and the position in the book.

• Very interesting indeed. Could you draw some more general conclusions? For example about the author, writing time, profitability, etc Jan 23 '19 at 8:35
• @Valorum - My goal here was literally wanting to know the average chapter length (ideally with some range to it, not just a single number). Conclusions are fun, but I think it would be overstepping my bounds here. Though what my data shows is that the bigger books not only have more chapters but longer length ones, and they tend to be longest towards the middle of the book.
– ibid
Jan 23 '19 at 10:32
• You've not gonna believe this, but I was up to Prisoner of Azkaban doing individual word counts of all of the Pottermore ePubs myself! Can't remember exactly how I got Excel to calculate my standard deviation but it wasn't just using a built in function, I had to mess around with a few functions together to get the weighted one. Yours is about double mine, so I wonder if I factored a half into it accidentally.
– Ongo
Jan 23 '19 at 15:59
• @Ongo - But how would you calculate standard deviation without even knowing all the chapter lengths? Unless I'm really misunderstanding how statistics works that seems completely impossible given your data.
– ibid
Jan 23 '19 at 21:02

For the series as a whole, we can tabulate the number of chapters and length of the books, and find the weighted average of the length of a chapter (read this to see what a weighted average is and why you can't just take an "average of averages"). An Excel spreadsheet of my own devising. The number bold and in blue is the weighted average it calculated.

So the weighted average chapter length across the whole series is 5542 words (rounded to the nearest whole word). If I had a source to determine the word length per chapter of each book, we could find a weighted average per book and then take a weighted average of that, but I don't imagine that'd stray too far from the 5542 calculated here.

Standard deviation is a little trickier, as with all of the different books to consider a weighted standard deviation would be more appropriate. After much toiling in Excel with the equation, I finally got a result of 747 (rounded to the nearest whole word, 746.5898815 exactly).

With these values, we can get a lovely normal distribution. Using the weighted mean and weighted standard deviation, the chapter length can be normally distributed (see link at bottom to do this yourself). In this image, we can see that the probability of a chapter having more than 6000 words is about 27%.

Not sure how useful they'll be for you, but anyway the quartiles are as follows (nearest whole word):
Q1 = 5038
Q2 = 5542
Q3 = 6045