Milesight Smart Tools, the IPC/NVR Calculator software can be used to calculate the number of NVRs needed to manage the available IP cameras, and calculate the number of IP cameras which can be connected to the specified NVRs. By this tools, you can calculate the storage space you need according to the camera recording time and specified configration. And the recording time how long you can use for all the cameras before the HDD become full is also available according to this tools.