01
Bitrate, not megapixels
A 4 MP camera at H.265 writes about 4 Mbit a second, which is 43 GB a day if it never stops. Everything else on this page follows from that one figure.
- ÷ 8 for bytes, × 86 400 for a day
Calculator
Terabytes, watts, and how many days it keeps.
Thirty-one camera and network SKUs in the shop, and until now no way to work out which of them you need.
- H.265, real-world bitrates
- Sizing, not a quote
116
Higher is not automatically better: 4 MP on a 2.8 mm lens sees a face at the gate; 8 MP across a whole garden sees eight megapixels of lawn.
Motion-only on a street-facing camera is nothing like the 5 % the brochures imply — 35 % is closer, and that is what is used here.
3 days90 days
Fourteen is the usual ask. Thirty is what an insurer sometimes wants in writing.
H.265, medium quality, normal movement. Bitrates are what VIGI cameras actually stream at, not the best case on the box.
Disk you need
2.25 TB
Fills, per day
161 GB
Per camera
27 GB
Fit a disk of
4 TB
Which holds
25 days
Recorder
8-channel
PoE budget
53 W
The cameras draw 42 W; with 25 % headroom that wants a 8-port PoE, 110 W switch. Headroom is not padding — a switch run at its ceiling browns out the last camera on a cold morning when every infrared illuminator is on at once.
That is more than one switch can carry. It is a normal answer at this size — two switches, or one with a higher budget and a separate run — and it is the point at which this stops being a form and starts being a site visit.
Above about 10 TB it is worth two disks rather than one, so a failure costs you half the footage instead of all of it.
The period you chose
The others
Cameras
Headroom
What decides the number
Four things, and only one of them is the camera.
02
How much of the day it writes
Continuous is continuous. Motion recording on a street-facing camera is about a third of the day, not the 5 % a brochure implies.
- 35 % assumed for motion
- 62 % for the mixed mode
03
Watts, and headroom over them
Six watts a dome, twelve for a varifocal or a zoom. Add a quarter on top or the last camera on the switch is the one that fails in winter.
- 25 % headroom, always
What this leads to
The next question this one raises.
Network sizing
The switch above is part of a network. This sizes the rest of it.
What happens in an outage
Cameras that stop recording when the street goes dark.
What we fit and why
Lenses, placement, and what holds up as evidence.
The cameras themselves
Every camera in the shop, with its lens and its draw.
Start here
Want this sized on site instead?
The assessment includes walking the property and marking the camera positions. It is free, and it is where the real number comes from.