Implementations described and claimed herein provide systems and methods for estimating migration progress. In one implementation, a target file system is initialized to which to migrate existing data from a source file system. An initial amount of data to be migrated to the target file system is estimated based on an examination of in-use space at a root of the source file system. Any mount points for nested file systems in the source file system are identified. An amount of data for each of the nested file systems is estimated based on an examination of in-use space at the mount point for the nested file system. An estimated total amount of data to be migrated from the source file system to the target file system is determined based on the initial amount of data to be migrated and the amount of data for each of the nested file systems.