Clozemaster boasts thousands of sentences in over 50 languages. But the number of sentences can seem like a rather meaningless metric. Just what does it mean to play 1,000 sentences on Clozemaster? Is that a lot or a little? Have I made significant progress, or am I fooling myself? How about 5,000 sentences? 10,000?

What we need is a reference point, a number that almost everyone can relate to and that allows us to give meaning to the sentence counts on Clozemaster.

Most people across the world have heard of, if not read or seen, Harry Potter. Harry Potter and The Sorcerer’s Stone by J.K. Rowling (1998), the first book in the series, has 6,619 sentences. We can use this number, 6,619 sentences, as our reference point.

So! The Fluency Fast Track contains one sentence for each unique missing word, or “cloze word” for a given language on Clozemaster. If you were to complete the Fluency Fast Track on Clozemaster for Spanish, 25,394 sentences, it would be roughly equivalent to reading Harry Potter and The Sorcerer’s Stone 3.83 times, one sentence at a time. In other words a 3.83 on the Harry Potter Index. And not only is it equivalent to reading Harry Potter more than 3 times, but you see a new word with each sentence played on the Fast Track.

Of course this comparison isn’t exact — the number of words per sentence is different, and the number of sentences differs by language. And there’s the larger context and continuity to be gained reading a book. But! It’s a still a valuable reference point. Even if we round down significantly, reading the equivalent of Harry Potter just once in your target language is a huge step towards improving your vocabulary and reading comprehension.

So how do other languages on Clozemaster rank on the Harry Potter Index? For English speakers:

German Fast Track : 28,456 sentences, or the equivalent of reading Harry Potter and The Sorcerer’s Stone 4.29 times, or a 4.29 on the Harry Potter Index (HPI)

: 28,456 sentences, or the equivalent of reading Harry Potter and The Sorcerer’s Stone 4.29 times, or a French Fast Track : 26,065 sentences; 3.93 HPI

: 26,065 sentences; Italian Fast Track : 21,303 sentences; 3.21 HPI

: 21,303 sentences; Russian Fast Track : 44,697 sentences; 6.75 HPI

: 44,697 sentences; Even for Icelandic you can play the equivalent number of sentences as in Harry Potter — 7,388 total sentences for Icelandic, plus some extra sentences with unknown difficulty levels

And now we know — the 1,974 sentences I’ve played so far on the French Fast Track is roughly equivalent to reading ⅓ of the first Harry Potter novel, one sentence at a time — pretty cool!