That would depend on what type you are talking about, there are both Madagascan leaf tails, the entire genus Uroplatus, and there are Australian leaftails of the genus Saltuarius. I believe that there are some 12 species in the former, and 7 in the later, plus subspecies and some undescribed species. I am probably wrong with these counts, because I am not an expert and they constantly change. Care requirements differ for each, as do sizes (from about 6 grams to 45 grams?). The only one I have any experience at all keeping is U. phantasticus, a single male, and I have a ~60 gallon terrarium for him- but they have been successfully kept and bred in 10 gallon tanks.
Sorry for the long winded answer, in short: it depends ^_^