It's open to debate, and that's part of the problem and fun with cataloguing such things accurately, but I've always believed there to be seven films in the Hammer "Dracula" cycle. Although "Brides of Dracula" has Dracula in its title, and good though it is, the Count's absence from this film surely excludes it from being part of the canon, strictly speaking. I include the two "modern" takes that Hammer took on the story. They reunite Lee as Dracula with Cushing as nemesis Van Helsing for the first time in the series since its début and thus give the feel of the cycle having come full circle.
Based on the aforementioned, this would make my personal favourite, "Taste the Blood of Dracula", the fourth of the seven and thus the middle film of the cycle. The "Frankenstein" series also comprises seven and its middle film, "Frankenstein Created Woman", covers the same territory as this Dracula movie, namely Victorian values and three aristocrats who get what's coming to them!!! I'm sure it wasn't planned this way, at least not from the outset, but there is a kind of beauty to viewing them with this sequence in mind. There is no lumbering monster in this Frankenstein film which makes it atypical of its series just as, without many of the familiar trappings we have come to expect such as priests, suspicious villagers and disgruntled coach drivers, "Taste the Blood of Dracula" is also atypical.
Alas, my argument isn't watertight! Although Dracula isn't mentioned in the title, in "The Legend of the Seven Golden Vampires", released by Hammer after their last "official" Dracula movie "The Satanic Rites of Dracula", the character is included although this time not played by Christopher Lee. Therefore, it could be argued there are eight films in the cycle, nine if one still wishes to include "Brides of Dracula", and therein lies the problem. It is impossible, however desirable, to pin an exact number of films to the sequence!