Plan the coverage before you buy the cameras
Work out what a camera can actually see, before you spend a thousand dollars finding out.
Most security camera advice stops at "get 4K". That is not an answer. How many cameras a house needs, how many days a drive holds, what a switch has to supply, and how far a given lens can still identify a face are all calculable, and the answers decide what you should buy.
Start with the number you actually need
Fifteen calculators, each showing its formula and saying plainly whether it rests on a published standard or an industry convention. Where a figure cannot be computed honestly from what manufacturers publish, they say so rather than showing a zero.
- Convention
How Many Security Cameras Do I Need?
Work out how many security cameras a house needs from its entry points rather than its floor area, and see the recorder, storage and PoE budget that follows.
- Convention
NVR Storage Calculator: How Many Days Will It Record?
Calculate how many days of footage a recorder holds from your camera count, resolution, codec and drive size, and the capacity a retention target needs.
- Standard
PoE Power Budget Calculator
Work out the switch power budget your cameras require under IEEE 802.3af, 802.3at and 802.3bt, and why it is larger than the cameras own draw.
- Convention
Security Camera Upload Bandwidth Calculator
Calculate the upload speed and monthly data a cloud camera system consumes, and what fraction of your home uplink it takes.
- Standard
DORI Distance Calculator
Calculate the distance at which a camera can detect, observe, recognise and identify a person, using the EN 62676-4 pixel per metre thresholds.
- Standard
Cloud Subscription vs Local NVR Cost Calculator
Compare the five year cost of a per-camera cloud subscription against buying a local recorder outright, and find the break-even point.
The standard nobody selling cameras mentions
DORI, defined in EN 62676-4, measures a camera in pixels per metre of the scene rather than in megapixels. It is the honest answer to "how far can this camera see", and it is why a 4K camera on a wide lens will record a burglary in perfect detail and still not identify anyone.
| DORI level | Pixels per metre | Maximum distance | What that gets you |
|---|---|---|---|
| Detect | 25 | 276 ft | Something is there, and it is a person rather than an animal or a shadow. |
| Observe | 62.5 | 110 ft | Clothing and behaviour are visible. You can follow what someone is doing. |
| Recognise | 125 | 55 ft | You can tell whether this is someone you already know. |
| Identify | 250 | 28 ft | A stranger can be identified from the footage to an evidential standard. |
Work it out for your own camera or read the standard explained
Complete systems, not a shopping list
Six full builds across two ladders, wired and wireless, each listing every camera, drive, switch, cable, connector and tool needed to finish the job, with a live running total. Each one also says what you can skip and who should not buy it.
- Beginner
Beginner 4 Camera PoE System
The lowest total cost to a system that records continuously and needs no subscription.
- Intermediate
Intermediate 8 Camera 4K System
The best value per dollar across coverage, resolution and retention. This is the build most people should make.
- Expert
Expert 16 Camera Property System
The performance ceiling: identification at range, thirty day retention and a network the cameras cannot reach out of.
- Beginner
Renter Friendly No Drill Wireless System
Recording without drilling, without a subscription, and without leaving anything permanent behind.
- Intermediate
Long Driveway and Gate Coverage
Identification at range on a single long approach, rather than coverage everywhere.
- Beginner
Doorbell and Entry Starter
The smallest spend that produces a system worth having, with nothing that has to be thrown away later.
Answers for your exact configuration
188 pages working through every combination of camera count, resolution, lens, drive size, PoE class and cable length, so the answer for your setup already exists rather than needing to be derived from a general article.
-
DORI distance
25 pages
-
NVR storage days
30 pages
-
PoE power budget
18 pages
-
Upload bandwidth
24 pages
-
Lens coverage
35 pages
-
How many cameras
18 pages
-
Cable run limits
18 pages
-
microSD recording days
20 pages
Read before you buy
-
Best home security cameras and systems by category
Every roundup here presents a beginner, an intermediate and an expert pick rather than one flat list, because that is how people actually shop for a system they will live with for years.
18 pages
-
Head to head comparisons
The specific choices people get stuck on, with the numbers that actually decide them rather than a feature grid.
8 pages
-
Home security camera guides
How the parts fit together: placement, wiring, recording, the network, and the law that applies to all of it.
24 pages
-
Reference charts and tables
The tables worth bookmarking. DORI thresholds, PoE classes, bitrate by resolution, cable limits and storage by camera count.
14 pages
-
Camera and recorder reviews
What the published specifications actually mean for a real property, based on manufacturer documentation and verified owner reports rather than on hands-on testing we did not do.
9 pages
Get the system planning sheet
The camera count, storage and PoE budget worksheet, plus the wiring checklist, as one printable page.
A camera is a legal instrument as well as a technical one. Aim cameras at your own property and your own boundary, never into a neighbour's windows. Cameras in bedrooms, bathrooms or anywhere with a reasonable expectation of privacy are a serious legal problem, including for guests, lodgers and anyone who works in your home. Audio is legally different from video, many US states require the consent of every party to a recorded conversation, and several recorders capture audio by default, so check your own state before enabling it. Some jurisdictions require visible notice that recording is taking place, and landlords and homeowner associations often add their own rules. This is researched general information and not legal advice.
And a camera is a computer on your network. Change every default password, keep firmware updated, and understand that a cloud camera means a third party holds recordings of your home. A local recorder keeps them in the building, which is a genuine buying consideration rather than a technicality.