Here’s a link to a disc space calculator. I set my frame rate to 15 for indoor and 25 for out door on the 2 4mp cameras. I estimated 16 hours continuous record and the remaining 8 motion detection. 6:00am to 10:00 pm since it’s a co-share work space. This will give me 4 weeks of storage. The NVR I purchased has room and can use up to 2, 6TB drives if I need more.
http://www.hikvision.com/us/download_more_82_i4692.html