Formula
Cameras × Mbps ÷ 8 × recording seconds × retention days × headroom, converted from bytes to decimal TB and binary TiB.
Motion recording: Savings depend on the scene, sensitivity, and activity. Use the 24/7 result as an upper comparison, then correct it with a week of measured usage.
Why TB and TiB differ
Drive vendors define 1 TB as 10¹² bytes. Binary units use 2⁴⁰ bytes per TiB, so the same byte count appears smaller when expressed in TiB.
Scenario comparison
Results compare the recording hours you enter with a 24/7 continuous upper case. Motion-active hours vary by location, season, and sensitivity, so do not treat the apparent saving as guaranteed.
Worked examples
| Setup | Example inputs | Check before buying |
|---|---|---|
| Two entrance cameras | 2 cameras · 2 Mbps · 12 h · 30 days | Include night noise and busy periods |
| Four home perimeter cameras | 4 cameras · 4 Mbps · 24 h · 30 days | About 5.70 TB as the continuous upper case |
| Eight-camera small shop | 8 cameras · 4 Mbps · 16 h · 45 days | Check after-hours policy and NVR capacity limits |
Next step
Read how codecs, frame rate, and motion recording affect retention.