NVR Storage Calculator: How Many Terabytes Do You Need?
Channels × bitrate × hours × days, plus the overhead installers forget — then the HDD combination, incoming bandwidth and the NVR models with enough bays to hold it.
Engineering tool · H.265 / H.264 bitrate references · Updated September 2026
Calculator
Pick the resolution and codec to load a typical main-stream bitrate, or type the exact figure from the camera's stream settings.
How the calculation works
Storage per channel per day = bitrate (Mbps) ÷ 8 × 3600 × recording hours ÷ 1024 = GB/day.
Multiply by channels and retention days, then add overhead (default 10%) for the file system, index and the fact that a 8 TB drive formats to about 7.3 TB. The result is the usable capacity you must install, not the marketing size.
Bitrate is the number that moves the answer most. H.265 halves H.264 at the same quality; smart codecs (H.265+, Ultra 265) cut a further 30–50% on static scenes but save little on busy roads. Variable bitrate at night with IR noise is where most 'the disk filled up early' calls come from.
The second limit is bandwidth: the NVR must accept channels × bitrate as incoming Mbps and play back what it records. The calculator shows the incoming figure so you can check it against the model page before ordering.
Bitrate reference (main stream, H.265)
Medium motion, 15–20 fps, default quality. Doubling frame rate or quality roughly doubles the bitrate.
| Resolution | H.265 | H.264 | Storage / channel / day (24 h) |
|---|---|---|---|
| 2 MP (1080p) | 2 Mbps | 4 Mbps | ≈ 21 GB |
| 4 MP | 3 Mbps | 6 Mbps | ≈ 32 GB |
| 5 MP | 4 Mbps | 8 Mbps | ≈ 42 GB |
| 8 MP (4K) | 6 Mbps | 12 Mbps | ≈ 63 GB |
| 12 MP | 10 Mbps | 20 Mbps | ≈ 105 GB |
Five rules that keep the recorder from filling up early
Each one comes from a real 'we only have 12 days, you promised 30' call.
- Size on the night-time bitrate, not the daytime one — IR noise can double it on cheap sensors.
- Use surveillance-grade drives (workload 180–550 TB/year) — desktop drives fail early under 24/7 writes.
- Motion-only recording cuts storage 40–70% on quiet sites but almost nothing on a busy street — set hours/day honestly.
- Keep one bay free on 4-bay and larger NVRs — adding retention later is a hard-drive purchase, not a recorder replacement.
- Check incoming bandwidth and decoding capacity on the model page — a 32-channel NVR does not always record 32 × 4K.
NVR models by channels and drive bays
The models the calculator chooses from. Maximum channels and bays per datasheet; PoE variants power the cameras directly.
Questions installers ask
Short answers you can quote to your own customers.
How much storage does one 4 MP camera use per day?
About 32 GB at 3 Mbps H.265 recording 24 hours. Sixteen such cameras for 30 days need roughly 15.4 TB usable — two 8 TB surveillance drives.
Should I use one big drive or several smaller ones?
On 2-bay and larger NVRs, two drives of half the size cost about the same and keep half the footage if one fails. On 1-bay recorders buy the largest surveillance drive the model supports (typically 10 TB).
Does H.265 really halve the storage?
At the same visual quality, yes — roughly 40–50% less than H.264. All Uniview and Uniarch cameras and NVRs we ship support H.265; make sure the camera stream is actually set to it.
What retention period do most projects use?
Retail and offices 15–30 days, warehouses and factories 30–60 days, banks, casinos and some public tenders 90 days or more. Check the local regulation or tender document before you size.
Can you ship the NVR with drives installed and configured?
Yes — every NVR we ship can go out with surveillance drives fitted, formatted and the recording schedule set, so the installer only adds cameras. Send the channel count and retention days on WhatsApp for a quotation.
References
Standards and vendor documents this tool is based on. Product figures come from the datasheets on each model page; confirm the exact firmware and PoE mode with us before ordering.
Want the drives installed before shipment?
Send the channel count, resolution and retention days — an engineer sizes the NVR and drives and replies within 24 hours with a quotation.