Home / NVR Storage Calculator
By Ali Zafar
NVR Storage Calculator
Enter your camera count, resolution, frame rate and how long you need to keep footage. This tool gives you an estimated storage size and the average 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. The per-day and per-camera figures above are before the buffer.
Bandwidth is an average with no headroom added. To size your switch and NVR network ports, use the IP Camera Bandwidth Calculator.
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.
Have cameras with different resolutions or settings? Calculate each camera or group of identical cameras separately and add the results together.
Worked example
Illustrative only — your result depends on your own camera count, resolution, frame rate, codec, recording mode and retention. This example uses the calculator's default inputs: 8 cameras, 4MP, 15 fps, H.265, continuous 24/7 recording, 30-day retention.
| Step | Result |
|---|---|
| Frame-rate factor | 0.3 + 0.7 × (15 ÷ 30) = 0.65 |
| Per-camera bitrate | 6 Mbps × 0.65 × 0.5 (H.265) = 1.95 Mbps |
| Average bandwidth, all cameras | 1.95 Mbps × 8 cameras = 15.6 Mbps |
| Storage per camera per day | (1.95 ÷ 8) × 86,400 ÷ 1,000 ≈ 21.06 GB |
| Storage, all cameras per day | 21.06 GB × 8 cameras ≈ 168.5 GB |
| Storage per camera, full retention | 21.06 GB × 30 days ≈ 631.8 GB |
| Total before buffer | 631.8 GB × 8 cameras ≈ 5,054 GB ≈ 5.05 TB |
| Headline figure, incl. 10% buffer | 5.05 TB × 1.10 ≈ 5.56 TB → recommended drive: 6 TB |
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. As a planning approximation, this calculator scales bitrate between 30% and 100% of the 30fps figure, so 15fps is treated as about 65% of the 30fps bitrate rather than 50%. That keeps the estimate on the cautious side instead of underselling your storage needs. Real cameras vary with their I-frame (GOP) settings and the scene, so check your camera's datasheet or measure its actual stream — and enter that figure with the custom bitrate option if you have it.
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.
Source note: the roughly 50% figure for H.265 matches what the ITU said when it announced the standard, that HEVC "will need only half the bit rate of its predecessor" (ITU press release, 25 January 2013). That was a projection by the standards body, not a measurement of CCTV streams. The H.265+ and smart-codec savings used on this page are planning estimates without a verified source, and they vary heavily with the scene.
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, 24TB) 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. Drive labels and this calculator both use decimal units (1 TB = 1,000 GB); your NVR or operating system will usually show a smaller figure for the same drive — see the FAQ below.
Working backwards: how many days will a drive hold?
The same formula works in reverse. Take the "Storage per day (all cameras)" figure from the results, add the 10% buffer, and divide the drive's capacity by it: days ≈ drive capacity (GB) ÷ (storage per day × 1.10). In the worked example above, a 6 TB drive holds about 6,000 ÷ (168.5 × 1.10) ≈ 32 days at 24/7 recording. This calculator doesn't solve for retention days directly — run your setup, then divide.
Using that same default setup — 8 cameras, 4MP, 15 fps, H.265, continuous 24/7 recording (168.5 GB/day for all cameras) — a 1 TB drive holds about 1,000 ÷ (168.5 × 1.10) ≈ 5.4 days, and a 4 TB drive holds about 4,000 ÷ (168.5 × 1.10) ≈ 21.6 days. These figures are specific to this exact setup: change the camera count, resolution, fps, codec, bitrate, or recording mode/activity, and both the storage-per-day figure and the number of days a 1 TB or 4 TB drive lasts will change with it.
Frequently asked questions
How much storage does one camera use per day?
It depends on the camera's bitrate. Each 1 Mbps of continuous recording uses about 10.8 GB per day (1 ÷ 8 × 86,400 ÷ 1,000), so a steady 4 Mbps camera uses about 43.2 GB per day. With this calculator's default settings (4MP, 15 fps, H.265), one camera works out to about 1.95 Mbps, or roughly 21 GB per day of continuous recording.
Does H.265 reduce NVR storage requirements?
Yes. H.265 (HEVC) typically needs roughly half the bitrate of H.264 for comparable image quality, and H.265+ or other smart-codec modes can reduce it further on scenes with little motion. This calculator applies planning factors of 1.0 for H.264, 0.5 for H.265 and 0.32 for H.265+, so treat the result as an estimate — actual savings depend on the camera, the scene and the encoder.
Does motion-triggered recording reduce storage?
Yes, in principle. Motion-triggered recording only writes to disk when activity is detected, so less recording time means less storage used. The saving depends entirely on how busy the scene is, so the percentage in this calculator is an estimate you set (15–30% is typical), not a value the camera can guarantee. Network bandwidth is not reduced, because most IP cameras still stream to the NVR continuously.
How does frame rate affect NVR storage?
Lowering the frame rate reduces bitrate, but not in a straight line. As a planning approximation, this calculator scales bitrate between 30% and 100% of the 30 fps figure, so 15 fps is treated as about 65% of the 30 fps bitrate rather than 50%. Real cameras vary with their I-frame (GOP) settings and the scene, so check your camera's datasheet or measure its actual stream, and use the custom bitrate field if you have a measured figure.
Why does my drive show less capacity than advertised?
Drive manufacturers advertise capacity in decimal units (1 TB = 1,000 GB = 1,000,000,000,000 bytes), and this calculator uses the same convention. Operating systems and NVR firmware often report capacity in binary units, which shows a smaller number for the same drive, and formatting overhead reduces the usable amount further. A 6 TB drive showing roughly 5.45 TB is expected, not a fault.
Does this account for RAID?
No — the headline figure includes a 10% planning buffer for filesystem overhead and bitrate spikes, but it does not include RAID overhead. 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 one reason the 10% buffer is built into the drive recommendation. For long retention periods or busy scenes, add more margin.
What if my cameras have different resolutions or settings?
Calculate each camera or group of identical cameras separately, then add the TB results together before choosing a drive size. For example, run 4 cameras at 4MP and 4 cameras at 8MP as two calculations and add the two totals, rather than adding the two recommended drive sizes.
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 CCTV tools
With storage sized, the rest of the system is worth checking too. The IP Camera Bandwidth Calculator handles your switch uplink, the CCTV Storage Calculator covers any analog HD-CCTV cameras on the job, and the Field of View Calculator confirms placement and coverage before you finalize the install.
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.