How to work out camera storage and bandwidth

Resolution sets an upper bound. Bitrate is what reaches the disk, and it is the only number the calculation needs.

"How much storage does a 4K camera need?" has no answer. Two 4K cameras can differ by a factor of five depending on codec, compression setting, frame rate and how much the scene moves.

A camera watching an empty corridor at night compresses to almost nothing. The same camera watching a car park full of moving trees in daylight produces many times more. What actually reaches the disk is the encoded bitrate.

The arithmetic

Storage per day = bitrate ÷ 8 × seconds recorded.

A 4 Mbit/s camera recording continuously: 4 ÷ 8 = 0.5 MB/s, times 86,400 seconds, is about 43 GB a day. Thirty days is roughly 1.3 TB. For one camera.

Sixteen of them is about 21 TB for the month, which is the number worth having before choosing a recorder rather than afterwards.

Get the bitrate from the camera

It is a setting you control and can read back. Estimating it from resolution is guessing at the one variable you do not have to guess at.

H.265 typically produces about half the bitrate of H.264 for comparable quality. If the cameras and the recorder both support it, that is the cheapest storage saving available — but check the recorder, because a mismatch means transcoding or no recording.

Where motion recording estimates go wrong

Recording only on motion saves a great deal on a quiet site and nothing at all on a windy day, when moving foliage and shadows trigger every camera continuously.

Size for the worst case you can tolerate rather than the average you expect. A system that overwrites a week early during the storm that produced the footage you needed has failed at the only moment it mattered.

The network figure that matters

Not each camera, but the total arriving at the recorder — and it is a steady load, not a peak. Sixteen cameras at 4 Mbit/s is 64 Mbit/s every second of every day.

On a 100 Mbit/s link that is most of the capacity gone permanently. On a gigabit link it is comfortable. And if the cameras share a switch with anything else, that traffic is competing with a constant stream rather than an occasional one.

Frequently asked questions

How much storage does a 4K camera need?

It depends on the bitrate, not the resolution. Read the bitrate off the camera and calculate from that — two 4K cameras can differ fivefold.

What is the formula?

Bitrate divided by 8 gives megabytes per second, multiplied by the seconds recorded per day. A 4 Mbit/s camera recording continuously uses about 43 GB a day.

Does H.265 halve the storage?

Roughly, for comparable quality. Check the recorder supports it too, or you will be transcoding or not recording.

Is motion-only recording reliable for sizing?

It saves a lot on a quiet site and nothing on a windy day. Size for the worst case, because the storm that fills the disk is usually the event you wanted the footage of.

How much bandwidth do cameras use?

The total arriving at the recorder, continuously. Sixteen cameras at 4 Mbit/s is a constant 64 Mbit/s, which is most of a 100 Mbit/s link permanently occupied.