Purgatory has 33 cantos and 4,755 lines, which comes to around 125 pages in an ordinary edition. The number varies with the edition, the page format and the notes, but this is the order of magnitude. Each canto takes up, on average, between three and four pages.
The estimate starts from the roughly 32,600 words of the Italian original and takes into account that verse, with its line breaks, takes up more page than prose. The three canticas are similar in size: Inferno has about 125 pages and Paradise about 123, so that the whole Comedy comes to around 370.
The site's Reading Schedule divides the work into two weeks, at about 9 pages a day. The first week runs from cantos I to XVI, up to Marco Lombardo, on the eve of the doctrine of love, and the second, from cantos XVII to XXXIII, from the center of the poem to Eunoe. That averages a little over two cantos a day.
Because it is poetry in terza rima, Purgatory reads more slowly than the page count suggests: the number of names and references calls for a pause at every note. Anyone who prefers a more relaxed pace can read one canto a day and stretch the reading over more weeks.