How many pilgrims are making the journey to Canterbury in The Canterbury Tales?

The second paragraph of the prologue records that there are originally 30 pilgrims who make their way to Canterbury. This includes the 29 pilgrims that the narrator meets at the Tabard Inn plus himself.

At nyght was come into that hostelrye
Wel nyne and twenty in a compaignye

Each of these people is making their way to the Shrine of St Thomas a Becket for his or her own personal and religious reasons, but they all decide to travel together for reasons of safety and for each others's company.
While they are not pilgrims themselves, there are three other members of this party. Harry Bailly, the host and innkeeper, decides to join in. Later, the Canon and his yeoman meet the traveling party and tag along. This brings the total number up to 33. Chaucer originally intended to have stories from each of the characters, but he died before he could complete his work.