This is a difficult question to answer because towns were of different sizes and the size of a guild depended on what kind of guild it was. For example, an association of bakers would have a lot more members than a guild of glovers. Florence had a population of about 20,000 people in 1100 A.D.. If we assume 1 baker per hundred people, that would be 200 men. Also, it is important to remember that guilds usually had a complex membership policy. So, you might spend years as a "probationer" before actually becoming a full member. Of course, Florence grew tremendously after this time because of its cloth industry. By 1330, right before the plague struck, there were about 200 companies making cloth in Florence. Approximately 30,000 people were estimated to be part of the trade, about a third of the full population of Florence at that time. If we assume each firm had several guild members, the membership in the guild may have between 800 and 1000 men. The book "A History of Florence 1200-1575" by John M. Najemy estimates that at this time Florence had 8,000 guild members total of whom 3,000 were in the textile trade and the Wool guild alone had 600-700 members. The same source states that at this time the shoemaker's guild had 1550 men in it. All of these figures ultimately derive from the Nuova Cronica by Giovanni Villani (1280–1348), one of the most important books of medieval history.