CCTV NVR Storage Calculator
Work out how much recording storage your cameras actually need — from resolution, frame rate, codec and retention — plus the RAID configuration and network bandwidth to support it.
Add a group per camera type. Mixed estates are normal — a few 4K cameras on entrances and 2MP elsewhere.
A quiet back office might be 10%. A busy loading bay or corridor is closer to 50–60%. Be generous — under-estimating activity is the most common way these numbers go wrong.
Check whether your sector or your insurer sets a minimum. 30 days is the common default; some regulated environments require 90.
These are sizing estimates, not a quotation. Real bitrates vary with scene detail, lighting and how each camera is configured.
Get this sized properly →How the numbers are worked out
Bitrate is what actually drives storage
Storage is bitrate × time. Nothing else matters nearly as much. A camera's bitrate comes from its resolution, its frame rate, the codec it encodes with, and how much movement is in the scene.
The estimate starts from a typical bitrate for each resolution at 15 fps on H.264, then adjusts for your frame rate, codec and scene activity. If you already know a camera's configured bitrate, enter it directly — that is always more accurate than any estimate.
Codec choice roughly halves it
H.265 (HEVC) needs about 45% less bitrate than H.264 for the same picture. Vendor "smart" variants — H.265+, Zipstream, and similar — go further again on static scenes by lowering the bitrate when nothing is moving.
The saving is real but scene-dependent: a camera watching a busy road will not compress nearly as well as one watching a locked store room.
Why usable is bigger than raw
Two things sit between raw footage and the drives you buy. RAID parity takes capacity for redundancy — one drive's worth for RAID 5, two for RAID 6, half of everything for RAID 10. Then a filesystem needs free space to work in, and an NVR needs room to overwrite cleanly rather than running to 100% full.
Drives are also sold in decimal terabytes, so an "8 TB" drive presents about 7.3 TiB. The disk count here already accounts for that.
Bandwidth matters as much as capacity
Every stream crosses the network before it lands on a disk. Aggregate bitrate tells you what the switch uplink and the NVR's network interface have to sustain — continuously, not in bursts.
Once the total approaches a gigabit, uplinks and NIC teaming need designing rather than assuming. If cameras are PoE-powered, the switch power budget needs checking too.