Security camera storage calculator
By Devin Chua · Data checked by Owen Nakamura · Updated Most camera-storage calculators stop at “you need X TB.” This one starts there: set your cameras, bitrate, retention and RAID level, and it works out the usable storage after RAID, the exact surveillance drives to buy, a recommended NAS, and the total cost in CAD — live from Amazon.ca. A 4K camera needs roughly 3.2 TB a month at H.265; below is your real number and what to buy for it.
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12.7 TB of footage over 30 days, +20% overhead = 15.2 TB
The formula, shown
Camera storage is simple arithmetic once you know the bitrate:
GB per day, per camera = bitrate (Mbps) × 3600 × hours ÷ 8 ÷ 1024. Multiply by your camera count and retention days for the footage size, add ~15–25% overhead for the filesystem, indexes and audio, then size the array so its usable capacity (after RAID parity) covers that total. The tool does every step; the honest catch is that the answer lives or dies on the bitrate, which depends on resolution, codec and scene.
Bitrate by resolution and codec
Typical real-world ranges (cited from manufacturer and installer references — verify against your camera’s stream settings). We use the midpoint; frame rate scales it from a 20 fps baseline.
| Resolution | Codec | Bitrate (Mbps) | GB/day (24/7, 1 cam) |
|---|---|---|---|
| 1080p (2MP) | H.264 | 4–6 (~5) | 53 GB |
| 1080p (2MP) | H.265 / HEVC | 2–3 (~2.5) | 26 GB |
| 2K / 4MP | H.264 | 8–10 (~9) | 95 GB |
| 2K / 4MP | H.265 / HEVC | 4–5 (~4.5) | 47 GB |
| 4K / 8MP | H.264 | 16–24 (~20) | 211 GB |
| 4K / 8MP | H.265 / HEVC | 8–12 (~10) | 105 GB |
Motion-only recording: the honest version
Motion-only recording can slash storage — but by far less than people hope. The saving equals the fraction of the day something actually moves in frame, and a busy street or a windy yard can trigger recording most of the day. A ~35% duty cycle is a reasonable default for a quiet scene, but it is scene-dependent, so the calculator lets you set it and treats it honestly. Note too that Frigateand similar record a detect window (a few seconds before and after an event), not raw motion, which changes the maths again — see Frigate storage requirements.
Why surveillance drives, not desktop or NAS drives
A recorder writes many camera streams continuously, 24/7 — a workload ordinary drives are not built for. WD Purple and Seagate SkyHawk surveillance drives are rated for exactly that: high sustained sequential write workloads (180 TB/year for the base lines, up to 550 for the Pro/AI tiers), with firmware (ATA streaming) that prioritises smooth recording over random-access speed, and support for many simultaneous streams. The calculator only ever recommends surveillance-rated drives — it will never silently substitute a desktop drive, because that distinction is the whole point.
Retention and what happens next
Retention requirements vary by use and, in some settings, by local rules — this is general guidance, not legal advice, so set the days you actually need. Once you have the number, the tool hands you the drives and a NAS; from there, the best NAS for surveillance ranks the models, and the surveillance builder walks the full setup.
Frequently asked questions
How much storage does a 4K security camera need?
About 105 GB a day recording continuously at a typical 4K H.265 bitrate of ~10 Mbps — roughly 3.2 TB a month per camera. With efficient H.265 encoding and motion-only recording that drops sharply; at older H.264 it doubles. The calculator above gives your exact figure from your bitrate, hours and retention.
How do you calculate NVR/NAS storage for cameras?
Storage (GB/day) = bitrate in Mbps × 3600 × hours ÷ 8 ÷ 1024, per camera. Multiply by the number of cameras and your retention days for the footage size, add ~15–25% overhead for filesystem and indexes, then size the RAID array so its usable capacity covers that total. The calculator does all of it, including the drives and NAS.
How long will 1 TB record for security cameras?
At 1080p H.265 (~2.5 Mbps), 1 TB holds roughly 37 days for one camera or about 9 days for four, recording 24/7. At 4K it is far less — about 9 days for one camera. Codec, bitrate and motion-only recording change it a lot; see the days-per-TB figures on our how-long-will-1TB-record page.
Do I need special drives for a surveillance NAS?
Yes — WD Purple or Seagate SkyHawk surveillance drives, not desktop or even standard NAS drives. They are rated for the constant, many-stream sequential writes an NVR produces, with firmware (ATA streaming) tuned to prioritise smooth recording and workload ratings for 24/7 duty. The calculator only ever recommends surveillance-rated drives.
Answer a specific question
- How long will 1 TB record security cameras?
- How much storage does a 4K camera need?
- Storage for 8 cameras for 30 days
- The NVR storage calculation formula
Devin Chua works out which drives, RAM and NVMe cache fit which NAS model at nasdrives.ca, and what the RAID choice means for usable capacity, checked against what is in stock on Amazon.ca.
Data checked by Owen Nakamura, Technical editor (data checking)