A system for capacity forecasting for backup storage comprises a processor and a memory. The processor is configured to calculate a set of linear regressions for subsets of a set of capacities at points in time. The processor is further configured to determine a selected linear regression from the set of linear regressions. The processor is further configured to forecast a full capacity time based at least in part of the selected linear regression. The memory is coupled to the processor and configured to provide the processor with instructions.