1. A method for capacity management in a deduplication computing storage environment by a processor device, comprising: estimating a deduplication storage capacity as a function of an expected deduplication ratio, the expected deduplication ratio being an aggregation of a current deduplication ratio and a configured deduplication ratio, the current deduplication ratio depending on data currently stored in deduplication storage, and the configured deduplication ratio being an estimate made at a configuration stage of the deduplication computing storage environment.