# Recording consumption on the Hdd

1. I want to set up an surveillance camera and start recording. I want to know which size of the HDD I need to get. My questions is

- If I record 720 x 480 ( 24 h x 30 days ) . How much data would that be in the HDD ?
- If I record 1280 x 720 ( 24 h x 30 days ) . How much data would that be in the HDD ?
- If I record 1920 x 1080 ( 24 h x 30 days ) . How much data would that be in the HDD ?

2. Filesize = bitrate * running time

So you need to determine the bitrate your camera records at (look in the manual. They probably have a chart in there that tells you how much data is used as well)
3. Let's say I record in 1 mbit. Does that mean that 1 (mbit/s) x 60 x 60 x 24 x 30 = 2592 000 mbit/s = 2592 Gbit/s . And here in order to convert it to Gbyte I need to divide it with 8 because when I read here I see that 1 mbyte is 8 mbit http://www.wisegeek.com/what-is-the-difference-between-mbps-and-mbps.htm

So it's 2592 / 8 = 324 Gbyte. Is that correct ?

So if I record in 1920x 1080 or in 1280 x 720 doesn't affect the consumption of the hdd ?
4. That's right

Resolution strictly speaking doesn't affect the bitrate (just look at the equation) , therefore doesn't affect how much you will consume . However, a larger video resolution will require a higher bitrate to maintain a certain level of quality . Surveillance camera footage is useless if you can't see anything - if everything is blurry or blocky full of compression artifacts

And remember, that most HDD's use MB or GB definitions on the advertising/packaging, but the OS usually measures in MiB or GiB definitions
5. Thanks for the explanation.

How can I know if 720 x 480 ,or 1280 x 720, or 1920 x 1080 it they are 1 mbit or 2 mbit rate ? Or I can maybe choose that ? And if I choose higher rate, does that mean that the picture is more clear ?
6. It should tell you in your manual . If your camera has those resolutions offered, usually the 1920x1080 will be the highest bitrate. And yes, higher bitrate usually means clearer picture if every thing else is the same. Check if it has different options for setting the bitrate

If it says nothing about bitrate in the manual, then do some tests and check the recordings

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