List of the largest cannon by caliber

This list contains all types of cannon through the ages listed in decreasing caliber size. For the purpose of this list, the development of large-calibre artillery can be divided into three periods, based on the kind of projectiles used, due to their dissimilar characteristics, and being practically incommensurable in terms of their bore size: Stone balls: Cannon of extraordinary bore, which fired stone balls, were first introduced at the turn of the 14th to 15th century in Western Europe.

Source: Wikipedia — List of the largest cannon by caliber (CC BY-SA 4.0)