Nursery pot sizes can be a little confusing. We generally refer to a pot using a volume name – like 1 Gallon. Unfortunately nursery industry volumes don’t always quite correspond to actual volumes that you may be used to from food or beverage sizes. Here are a few pictures that may help you judge pot sizes, especially from a relative perspective.
First is picture of pot sizes for smaller perennials.
This is a picture of pot sizes for larger perennials.
This is a picture of pot sizes for most of our shrubs and trees.