Your security camera’s bit rate is essentially the amount of data being transferred and used by the camera every second i.e the processing power of your camera. Bit rate is measured in Kilobytes per second or megabytes per second. 

Why your camera’s bit rate matters 

The better the processing power of your security camera, the better the quality of your footage. The reason why two CCTV cameras with the same resolution can look different is because of the camera bit rate. 

What’s a good bit rate?

The bit rate you will need for your security system will depend on the frame rate, compression and resolution you need.  For example, anything over 1.8 MPs is a good bit rate for 720P running at 30 FPS whereas 1.4MPS and above is good for 720P running at 25 FPS. For high resolution such as 4MPs, you will need a bit rate of at least 4MBPS to ensure quality. Compression also plays a major role in bit rate. A 4K bitrate with an H.264 compression would require 10mbs whereas security footage in the same resolution with H.265 compression would require only 5mbs.
To calculate your bit rate you can use this online calculator.