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Short version: most households need far less storage than the spec sheets imply, because most cameras only record when something moves. For a motion-triggered camera, a 64GB microSD card holds roughly two to four weeks of events in a normal residential position, and 128GB comfortably covers a busy one. If you want genuine round-the-clock recording, the unit of measurement changes entirely: budget about 1TB of recorder drive per two cameras for 1080p continuous, or per camera for 4K continuous, and expect weeks rather than months of history.
The reason storage advice varies so wildly is that four numbers drive the whole calculation, and product pages rarely state any of them: resolution, frame rate, how many events per day the camera records, and whether it records only events or continuously. Change one and the answer moves by an order of magnitude. What follows is the arithmetic for each of the three storage routes so you can size your own setup rather than guessing.
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Cloud Plan Retention: How Far Back Can You Look?
With a cloud plan you do not size storage at all. You buy a retention window, and the provider handles capacity. Typical consumer tiers keep somewhere between 30 and 180 days of history, with 30 or 60 days the most common entry-level figure and longer windows sitting on higher tiers or on business plans. Anything older than the window rolls off automatically.
Two things catch people out. The window applies to events rather than hours, so a quiet camera and a busy one get the same number of days but very different volumes of clip inside it. And some plans cap individual clip length, so a long incident arrives as several separate recordings rather than one file.
Cost matters more than capacity here. Single-camera plans generally run a few dollars a month, whole-household tiers ten to twenty, and over five years the subscription typically outweighs the hardware. That is the trade: no card to manage, no drive to fail, but a bill that never stops. If that does not appeal, the models built to record locally are collected in our guide to the best security cameras without a subscription.
MicroSD Card Sizing: The Actual Numbers
The direct answer: at a typical residential event volume of 20 to 40 recorded clips a day on a 2K camera, a 32GB card holds roughly one to two weeks, 64GB holds two to four weeks, and 128GB holds around a month to six weeks.
Here is where those figures come from. A 20 to 30 second clip from a 2K camera commonly runs 15 to 40MB depending on bitrate and how much of the frame moves. Call it 25MB. Thirty clips a day is about 750MB, which puts a usable 60GB of card at roughly 80 days on paper — and that gap is why published estimates look so optimistic next to what owners report.
Three things pull the real figure down hard. Busy positions record far more than thirty clips: a camera facing a sidewalk or a road can log several hundred events a day before activity zones are tightened, which turns weeks into days. Higher resolution and frame rate multiply the file size directly, so a 4K camera at 30fps writes several times the data of a 1080p camera at 15fps for the same event. And any pre-roll buffering, longer clip length or continuous-while-plugged-in mode adds hours of footage that the card was never sized for.
Practical guidance: buy 128GB if the camera supports it, choose a high-endurance card designed for continuous video rather than a cheap photo card, and confirm the maximum supported capacity in the manual first. Unbranded and standard cards are the single most common cause of recordings that silently stop working, and the failure is invisible until you go looking for a clip that was never written.
NVR and DVR Drive Sizing by Camera Count
A wired recorder system is the one route where storage is genuinely a purchase decision, because these systems usually record continuously and continuous recording is where the data volume lives.
Rough working figures for planning, at typical bitrates and continuous recording:
- 1TB — one or two 1080p cameras for two to four weeks, or a single 4K camera for well under a week. Adequate for a small setup, tight for anything more.
- 2TB — a four-camera 1080p system for around two to three weeks, or four 4K cameras for a handful of days. The most common shipped capacity in consumer kits.
- 4TB — a four to eight camera 1080p system for several weeks, or a four-camera 4K system for around a week to ten days.
- 8TB and up — what you need if the requirement is a month of continuous 4K across six or more cameras.
Two settings change these numbers more than the drive size does. Switching the recorder from continuous to motion-triggered recording on the low-traffic cameras, while leaving the entry and driveway on continuous, is the standard compromise and it often triples the effective history. Dropping frame rate from 30fps to 15fps on cameras where you only need identification rather than smooth motion roughly halves the write volume with very little practical loss.
One hardware note worth the small premium: buy a drive rated for surveillance duty rather than a desktop drive. Surveillance drives are specified for constant sequential writing across many streams, which is precisely what a recorder does and precisely what a desktop drive is not built for. The full picture on these systems, including how the recorder and cameras are matched, sits in our guide to NVR camera systems.
Working Out Your Own Number
The honest answer to how much storage you need starts with a question about how far back you want to be able to look. For most households the useful window is one to two weeks, because that covers a vacation, a delivery dispute or a package theft noticed a few days late. A month is generous. Anything beyond that is usually either a business requirement or an insurance one, and it is cheaper to satisfy by downloading the clips that matter than by buying a drive large enough to keep everything.
Then decide what actually needs to be recorded. Continuous coverage on every camera is the expensive option and it is rarely the useful one. Continuous on the entry and the driveway, motion-triggered everywhere else, and tight activity zones on all of them will give a longer usable history on a modest card or drive than default settings will give on a large one. For how retention plays out once your storage is chosen, see how long security cameras store footage.