About HomeSecurityCalc
This site exists because most home security camera advice stops at 'get 4K', and that is not an answer to any question worth asking.
What this site is
HomeSecurityCalc works out the calculable parts of a camera system: how many cameras a property needs, how many days a drive holds, what power budget a switch has to supply, how far a given sensor and lens can still identify a face, and what a cloud subscription really costs against a recorder you own outright.
Those are the questions with real answers, and they happen to be the questions that decide what you should buy. A camera specification sheet is close to meaningless until it is turned into a distance, a number of days, or a number of watts.
Where the numbers come from
Everything computed here rests on one of two things, and every page says which. Some pages rest on a published standard: the EN 62676-4 DORI thresholds for pixels per metre, the IEEE 802.3af, 802.3at and 802.3bt power classes, the ANSI/TIA-568 hundred metre Ethernet channel limit, and ordinary lens geometry. Those are not ours to adjust.
Other pages rest on an industry convention: one camera per entry point, typical bitrate for a given resolution, fourteen to thirty days as a sensible retention target. Those are useful habits rather than facts, and a reader is entitled to disagree with them. Labelling which is which is the difference between information and assertion.
What we refuse to do
We do not test products in person and we never claim to. Every recommendation here is researched from published manufacturer specifications and verified owner reports. Any site claiming hands-on trials of forty camera systems is telling you a story.
We return nothing rather than inventing a figure. If a manufacturer does not publish a camera's infrared range or its low light performance, this site says it is not published rather than estimating it. Every calculator here is built to say "not computable" instead of quietly showing a zero, because a reader planning a camera position around an invented number is the worst outcome this site could produce.
We leave products out. The product catalog deliberately excludes copper clad aluminium cable sold for powered runs, switches whose power budget cannot carry the cameras they are sold alongside, relabelled grey market recorders, refurbished units listed beside new stock, and the flood of unbranded network cameras with no firmware support path. An unpatched camera on a home network is a worse outcome than no camera.
How this site is paid for
Through Amazon affiliate commissions on products readers choose to buy. That never changes which product gets recommended, and it is the reason the honest answer on several pages here is that you should buy less than you were planning to. See the affiliate disclosure for the full explanation.
Contact
Corrections are genuinely welcome, particularly on anything numerical. If something here is wrong, tell us and it gets fixed.