Embodiments of the present invention provide methods, program products, and systems for determining an amount of usable storage in a backup environment. Embodiments of the present invention can be used to receive system information pertaining to a storage backup environment. Embodiments of the present invention can calculate a compression ratio of the storage on a backup server and a backup ratio between an amount of data on a client computer system and an amount of data on the backup server and calculate an average amount of storage consumed on the backup server. Embodiments of the present invention can determine an existing backup capacity for the storage backup environment by identifying an amount representing the actual capacity of data capable of being stored on the backup server and reducing the amount representing the actual capacity according to the calculated average amount of storage consumed on the backup server.