Virtual machine capacity planning techniques are disclosed. In various embodiments, a set of time series data is constructed based at least in part on virtual machine related metric values observed with respect to a virtual machine during a training period. The constructed time series data is used to build a forecast model for the virtual machine. The forecast model is used to forecast future values for one or more of the virtual machine related metrics. The forecasted future values are used to determine whether an alert condition is predicted to be met.