How Long Do Security Cameras Keep Footage?
Most people find out how much their recorder holds on the day they need footage from last week. Here's how to work it out before then.
Updated · DCSI, Inc., Lutz FL
A camera recorder (an NVR, for IP cameras) writes video to a hard drive until the drive is full, then overwrites the oldest footage. How many days that takes is retention, and it is set by three numbers: how many cameras, how much data each one writes, and how big the drive is.
The rule of thumb that makes the math easy: one megabit per second, sustained for a day, is about 10.8 gigabytes.
Worked Examples
Continuous recording, before any motion-only savings. Real bitrates vary by camera and scene; these show the order of magnitude.
| Setup | Per day | Drive | Days kept |
|---|---|---|---|
| 4 cameras · 4 Mbps | ≈ 173 GB | 4 TB | ≈ 23 days |
| 8 cameras · 4 Mbps | ≈ 346 GB | 4 TB | ≈ 11 days |
| 8 cameras · 4 Mbps | ≈ 346 GB | 8 TB | ≈ 23 days |
| 8 cameras · 8 Mbps | ≈ 691 GB | 8 TB | ≈ 11 days |
| 16 cameras · 4 Mbps | ≈ 691 GB | 12 TB | ≈ 17 days |
What Changes the Number
Bitrate, not resolution, is what fills the drive
Resolution sets the ceiling; bitrate is what the camera actually writes. Two 4K cameras can differ by half depending on compression and settings. The recorder shows each camera's bitrate, and that's the number to plan from.
Compression
H.265 typically produces noticeably smaller files than older H.264 at similar quality. Most current IP cameras and NVRs support it, but older recorders may not.
Scene activity
A camera watching a busy street, moving palm fronds, or a pool with rippling water produces more data than one watching a still hallway. Wind and rain make it worse.
Continuous vs. event recording
Recording only on motion can stretch storage several times over. The trade-off is that you lose the moments before and between events, which is sometimes exactly what an investigation needs.
Frame rate
Security video rarely needs 30 frames per second. Dropping to 15 or so roughly halves the data on many cameras with little loss of usefulness for identification.
How Much Is Enough
Plan backward from how incidents actually get noticed. A package goes missing and nobody checks for two days. A neighbor asks about a car that drove through the street last weekend. An insurance adjuster asks for footage a week after a claim. For most homes, two weeks is a practical minimum and thirty days is comfortable. For businesses, check what your insurer or landlord requires first.
Retention is one input in a camera design, alongside how many cameras and where. Our guide to camera count covers placement, and our camera systems page covers what we install.
Camera Storage Questions
How long do security cameras keep footage?
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It depends entirely on the recorder's storage and how the cameras are configured. A typical home NVR recording eight cameras continuously keeps somewhere from one to several weeks before it starts overwriting the oldest footage. Recording on motion only, or adding storage, extends that.
How much footage should a home security system keep?
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Two weeks is a practical minimum for most homes, and thirty days is a comfortable target. Many incidents — a package theft, a damaged car, an insurance claim — aren't noticed or reported for several days, and footage that overwrote itself on day five is no help.
How do I calculate security camera storage?
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Multiply each camera's bitrate in megabits per second by 10.8 to get gigabytes per day, add the cameras together, and divide the drive size by that total. For example, eight cameras at 4 Mbps write about 346 GB a day, so a 4 TB drive holds roughly eleven days of continuous recording.
Is cloud storage better than an NVR for security cameras?
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Cloud storage survives the recorder being stolen or destroyed, but it usually costs a monthly fee per camera and depends on your internet upload speed. A local NVR has no per-camera fee and records through an internet outage. Hiding the NVR or putting it in a locked cabinet addresses most of its risk.
Do businesses need to keep camera footage longer?
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Often. Insurance carriers, landlords, franchise agreements, and some industries set their own retention requirements. Check those before sizing a commercial recorder rather than after.
Keep Reading
All guidesHow Many Security Cameras Does a House Need?
Counting cameras by approach rather than by wall, plus PoE vs. Wi-Fi, resolution, and retention.
Hurricane Season Security Checklist for Florida Homes
Keeping an alarm and cameras working through an outage, an evacuation, and the week after a storm.
DIY vs. Professionally Installed Security Systems
What a self-install kit does well, where it falls short, and the questions that decide which one fits.
Need More Days on Your Recorder?
We'll check your cameras' actual bitrates, tune the settings, and size storage to the retention you need.