Free tool
CCTV storage calculator.
Enter the cameras, how they record and how many days to keep. See how much drive space the recorder needs, and which drives to buy.
How CCTV storage is worked out
A camera sends a steady stream of video, measured in megabits a second. Multiply it by the hours it records and the days you keep, and add up the cameras.
GB a day per camera = Mbps × 10.8 × hours recorded ÷ 24
1.Add the cameras
Their resolution, compression and frame rate. Bitrates start at the makers' figures.
2.Set the recording
Days to keep, hours a day, all the time or on motion, and drive protection.
3.Read the answer
How many TB to buy and which drives, or how many days your drives hold.
Starting bitrates at 15 frames a second
| Resolution | H.265 | H.264 | A day on H.265 |
|---|---|---|---|
| 2 MP, 1080p | 1.5 Mbps | 3 Mbps | 16.2 GB |
| 4 MP | 2 Mbps | 4 Mbps | 21.6 GB |
| 5 MP | 3 Mbps | 6 Mbps | 32.4 GB |
| 8 MP, 4K | 4 Mbps | 8 Mbps | 43.2 GB |
| 12 MP | 6 Mbps | 12 Mbps | 64.8 GB |
Worth knowing
Leave 10% spare
Bitrates climb at night and in rain, and a camera or two always gets added.
Protection uses space
RAID keeps footage when a drive fails, at the cost of a drive or more. The drive counts include it.
Check the recorder
Each takes so many cameras, Mbps and drives: a common 16 channel one takes 160 Mbps and 2 drives.
Need less?
Record on motion, lower the frame rate, use H.265 or a smart codec, or keep fewer days. Check any law or contract first.
H.265 halves the drives
The same picture on H.265 takes about half the space of H.264. Most recorders and cameras sold now have it.
Eight 4 MP cameras for 30 days: about 5.7 TB on H.265, 11.4 TB on H.264.
Where these figures come from
Bitrates and recorder limits come from a camera and recorder maker's own published charts and datasheets.
Bitrates and recorders
What a camera records at 15 frames a second, on average
4 MP: 2,176 kbps; 8 MP (3840 × 2160): 4,620 kbps (H.264+)
A common 16 channel recorder
16 cameras, 160 Mbps in, 2 drive bays
No maker publishes these as one rule, so they are NexVolt's working figures. Your recorder shows the real bitrate:
Common questions
How much storage do 8 cameras need for 30 days?
Eight 4 MP cameras on H.265 at the makers' recommended 2 Mbps, recording around the clock, fill 5.18 TB in 30 days. With 10% spare, buy about 5.7 TB: a single 6 TB drive holds it. On H.264 the same cameras need about 11.4 TB.
How many days will a 4 TB recorder hold?
With four 4 MP cameras on H.265 recording all the time, about 46 days. Choose "Days these drives hold" above, enter the drives and the cameras, and the calculator works it out for any recorder. The recorder then overwrites the oldest footage, so the drives never fill up and stop.
How much does H.265 save over H.264?
About half for the same picture: the makers recommend 2 Mbps for a 4 MP camera on H.265 against 4 Mbps on H.264. Smart codecs (H.265+, Zipstream, WiseStream) save more on quiet scenes. Check the recorder supports the codec before you count on it.
Does motion recording save space?
Yes, a lot on a quiet site. The same eight cameras recording only when there is motion, about 30% of the time, need about 1.71 TB for 30 days. But motion is a guess, every event keeps a few seconds before and after, and a busy week can fill the drives early. Size for continuous recording if the footage matters.
Which RAID level should an NVR use?
RAID 5 survives one failed drive and gives up one drive's worth of space; RAID 6 survives two and gives up two; RAID 10 mirrors every drive and gives up half. For the eight cameras above on 4 TB drives, RAID 5 takes 3 drives. Many small recorders have only two bays and no RAID at all, which is why the recorder check matters.
Why does my 8 TB drive show as 7.3 TB?
Drive makers count a terabyte as 1,000,000,000,000 bytes; recorders and computers count in powers of 1,024. Same space, different units. The calculator works in the decimal TB printed on the drive, so its answer matches what you buy.
How many cameras can one recorder take?
As many as its channels, its incoming bandwidth and its drive bays allow, whichever runs out first. A common 16 channel recorder takes 160 Mbps and 2 drives: enough bandwidth for 40 4 MP cameras on H.264, but only 16 channels. Pick the recorder above and the calculator flags whichever limit the job passes.
Do I need surveillance hard drives?
Yes. A recorder writes all day, every day, from many cameras at once. Surveillance drives (WD Purple, Seagate SkyHawk and the like) are built and warranted for that; desktop drives are not, and fail sooner under it. Buy the size the calculator gives in a surveillance line.
