A bonsai can be any size as long as it is potted and has the appearance of a full-size specimen tree. Sizes of bonsai can range in height from no more than 2.5 cms (1 inch) up to about 2.2 meters (4 feet) although, in reality, there is no prescribed limit.
There are 4 general classifications (Large, medium, small, tiny) and each of these size classifications are split into several sub-sizes. However, not all sources agree on the exact sizes and names of the individual size categories, so you will find many variances in published sources and on the web. Below is a sample but be prepared to come across other variants.
Large Size Bonsai (Dai or Daiza)
Sub-classification : Imperial - Up to 200cms, Bonju - 100cm to 150cm tall, Omono 80-120cms tall.
Medium Size (Kifu)
Sub-classification : Chu/Chuhin - medium to large, 40 to 60 cms tal, l Katade-mochi, up to 40cms
Small Bonsai (Shohin)
Sub-classification : Myabi - 15 to 25cms. Gafu - 13 to 20cm Komono - up to 18cm
MameShito - 2.5 to 7.5 cms tall. Keshi - tsubu, up to 2.5cms.