DVR Day Calculator
What is the capacity on your hard drive? (in GB) Please Enter Hard Drive Capacity
Number of cameras recording?
Number of frames per second you would like each camera to record?
How many hours per day does the facility operate?
How many days of the week does the facility operate? 
Approximate Storage Time:

1 frame per second is the lowest frame rate recordable and 30 frames per second is the maximum which is real time
There is no real need to record in real time unless there are regulatory reasons as in case of government facilities or casinos
Recording at 1 frame per second is what traditional analog systems record
You can always rewind in high speed so the lower the frame rate the faster it is to playback an entire day
At 3 - 5 frames per second recording you will not miss any activity (remember this is per second)