Bitrate will affect the recording file size.
The higher the bitrate is, the better image and audio quality will be, and the bigger the file size will be.
The lower the bitrate is, the image and audio quality and file size will show the opposite results.
The way of calculating the recording file size is shown below:
Bitrate (kb/s, Bitrate/8)
24(hour, 1 day)
(PS: 1T=1024GB / 1G=1024MB / 1MB=1024KB)
Example: 1080P camera, Record 1 day , 1 Channel（normally 1080P Bitrate is 2048kb/s）
2048/8 x 3600 x 24 x 1 x 1 = 21G
Example: 4MP camera, Record 1 day , 1 Channel（normally 4MP Bitrate is 6144kb/s）
6144/8 x 3600 x 24 x 1 x 1 = 63.28G
So Reolink 4MP NVR with 2TB Built-in HDD, it can support 4CH 4MP camera recording for 8 days.
If you want to save the space, you can lower the bitrate to record a long time.