CCTV Storage & HDD Calculator (NVR/DVR)

How to Use the CCTV Storage Calculator

Add a camera group for each location or camera type in your system — for example, "Main Entry (4× 4MP)" and "Car Park (8× 8MP)". For each group, set the resolution, frame rate, compression codec, how many hours per day the cameras are actively recording, and the required retention period. The calculator sums across all groups to give you total daily storage consumption, required bandwidth, and a drive recommendation.

Use the Global Retention field at the top to apply the same retention period to all groups at once, or set different values per group for mixed-retention systems — for example, 90 days for entrance cameras and 14 days for internal corridors.

How Camera Resolution Affects Storage

Resolution is the biggest single factor in storage consumption. An 8MP (4K) camera at the same frame rate and compression as a 2MP (1080p) camera requires roughly four times the storage, because it captures four times as many pixels per frame. For large camera counts, moving from 4MP to 8MP across the board can double your total storage requirement.

This calculator uses the following base bitrates at H.264, 30 FPS, as representative industry averages for typical security camera encoders: 1MP (720p) — 2 Mbps; 2MP (1080p) — 4 Mbps; 4MP — 8 Mbps; 8MP (4K) — 16 Mbps. Actual bitrates vary by manufacturer and scene complexity — high-movement scenes (roads, busy entrances) will encode at higher bitrates than static indoor locations.

H.264 vs H.265 vs H.265+ — Storage Impact

Compression codec is the most effective way to reduce storage without changing resolution or frame rate. H.265 (HEVC) achieves approximately the same image quality as H.264 at around half the bitrate. H.265+ (Hikvision's smart codec, also marketed as Smart H.265 by other manufacturers) adds scene-adaptive encoding on top of H.265, typically reducing bitrates by a further 30–40% compared to standard H.265 for static scenes — though the savings are smaller in high-motion environments.

In practical terms: a 16-camera 4MP system recording at 15 FPS for 30 days needs about 20.7TB with H.264, about 10.4TB with H.265 and about 7.26TB with H.265+, assuming a static scene. The days-per-TB table above shows the same ratio for a single camera.

Frame Rate and Recording Schedule

Frame rate scales storage linearly — 15 FPS stores exactly half as much as 30 FPS for the same resolution and codec. Most security applications do not require full 30 FPS. Forensic identification works reliably at 12–15 FPS. Perimeter detection is effective at 5–10 FPS. Reducing frame rate is one of the simplest ways to extend retention without upgrading drives.

The recording hours per day field accounts for systems that do not record continuously. Motion-triggered recording, scheduled recording windows, or after-hours-only configurations all reduce effective daily storage. Set this to 24h for always-on systems, or lower values for scheduled or motion-activated setups — for example, 8h for a business operating on fixed office hours.

Choosing the Right Surveillance HDD

Standard desktop hard drives are not rated for the write patterns of continuous CCTV recording. Surveillance-grade drives — such as the WD Purple or Seagate SkyHawk series — are designed for 24/7 multi-stream write workloads and typically carry a higher write endurance rating (TBW) and a longer warranty than desktop equivalents. Always use surveillance-rated drives in NVRs and DVRs.

For systems above 32TB, a RAID-configured NAS or a dedicated storage server provides both capacity and redundancy. The drive recommendation in this calculator is a starting point — factor in a 10–15% overhead above the calculated figure to account for filesystem metadata, reserved sectors, and future camera additions.

Sizing the network as well as the disks? The IP camera bandwidth calculator adds up the same camera bitrates in Mbps and MB/s and checks them against your uplink and your NVR's ingest limit.

Frequently Asked Questions