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NVR Storage Calculator
Enter your camera count, resolution, frame rate and how long you need to keep footage. This tool gives you the exact storage size and the network bandwidth those cameras will use — so you don't undersize the hard drive or overload the switch.
Your setup
Storage needed
Includes a 10% safety buffer for filesystem overhead and bitrate spikes.
How this calculator works
Storage size depends on five things: how many cameras you have, their resolution, frame rate, the compression codec, and how many days you need to keep footage. This tool estimates the bitrate each camera produces, then multiplies that by the number of seconds you'll actually be recording over your retention period.
Typical bitrates by resolution (H.264, 30fps baseline)
| Resolution | Approx. bitrate | Typical use |
|---|---|---|
| 2MP (1080p) | ~4 Mbps | Standard entry-level dome/bullet cameras |
| 4MP | ~6 Mbps | Most common choice for new residential/commercial installs |
| 5MP | ~7 Mbps | Better detail for wider coverage areas |
| 8MP (4K) | ~12 Mbps | License plate capture, large open areas, retail |
Lowering the frame rate reduces bitrate, but not in a straight line — a camera at 15fps typically still uses roughly 60–70% of its 30fps bitrate, since I-frames (full reference frames) still fire at the same interval regardless of fps. This calculator applies that curve rather than a simple linear scale, so the estimate stays realistic instead of underselling your storage needs.
H.264 vs. H.265 vs. H.265+
H.265 (HEVC) typically cuts bitrate by roughly 50% compared to H.264 at the same visual quality — most NVRs and cameras sold since around 2019 support it. H.265+ and other vendor "smart codec" variants (Hikvision's H.265+, Dahua's Smart H.265+) add scene-analysis on top, dropping bitrate further on static scenes — real-world savings of 60–80% over H.264 are common, though this varies heavily with how much motion is actually in the frame. Treat the H.265+ figure here as a reasonable planning estimate, not a guarantee — a busy parking lot will use more than a quiet hallway even on the same codec.
Continuous vs. motion-triggered recording
Continuous recording is the safest choice for anything used as evidence — motion detection can miss fast-moving subjects or fail in low light. Motion-triggered recording can cut your storage requirement by 70–85%, which matters most on long-retention jobs (90+ days) where drive cost adds up fast.
Choosing the right hard drive
Always buy a surveillance-rated drive (Western Digital Purple, Seagate SkyHawk, or similar) rather than a standard desktop drive — they're built for the sustained 24/7 write workload an NVR produces and handle many simultaneous camera streams without dropping frames. Round up to the next common drive size (1TB, 2TB, 4TB, 6TB, 8TB, 10TB, 12TB, 16TB, 18TB, 20TB, 22TB) and keep the 10% buffer this calculator adds — real-world footage rarely matches theoretical bitrate exactly, especially with busy scenes or lighting changes that spike bitrate temporarily.
Frequently asked questions
Does this account for RAID?
No — the figure above is raw usable storage. If you're using RAID 1, 5, or 6 for redundancy, you'll need additional drives beyond this number since RAID trades some capacity for fault tolerance.
What if my cameras use variable bitrate (VBR)?
Most IP cameras run VBR by default, which means actual usage fluctuates with scene complexity. The bitrates used in this calculator are realistic averages for VBR-encoded footage, not the absolute peak — which is exactly why the 10% buffer is built into the drive recommendation.
Got a mix of analog and IP cameras, or an older DVR?
Use the CCTV Storage Calculator instead — it covers analog HD-CCTV formats (D1, 960H, AHD/TVI/CVI) alongside IP resolutions in one tool.
Related guide
This calculator handles the formula — but 12 real-world factors regularly make the calculated number wrong on an actual job. See NVR Storage Calculation: 12 Mistakes That Leave You Short on Space for the full field checklist before you order a drive.
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