Use Google to Calculate Surveillance StorageBy John Honovich, Published on Jun 29, 2013
Manufacturer calculators are a bad crutch that can increase mistakes. They attempt to make it easy but gloss over key factors that tend to deliver wildly inaccurate results.
Here's a better way and you can use google to do it. Check this short video how:
Google lets you quickly get accurate estimates, presuming you know the appropriate bitrate.
And quite frankly, if you do not know the bit rates of your cameras, you should not be doing calculations at all.
Letting a manufacturer calculator silently pick a bitrate is a recipe for disaster because it cannot know what you should know (compression settings, what scene you are using the camera in, how the camera reacts to scene differences, etc.). Spend the (short amount of) time to test and learn the bit rate of your camera / setup and then you can quickly and easily estimate using Google.