CCTV Storage Calculator — HDD, bandwidth & retention sizing

Storage in bytes = (cameras × bitrate × seconds × duty_factor) ÷ 8. With cameras at 16, bitrate at 8 Mbps (Hikvision 4K H.265+), 30 days at 24/7 duty, that's (16 × 8,000,000 × 30 × 86400) ÷ 8 = 4.147 × 10^13 bytes = 41.5 TB. Terabytes here are decimal TB (10^12 bytes) — the same unit drive capacities are sold in, so the drive-count plan divides like by like. The tool adds your headroom (default 20%) on top, so the recommendation lands near 49.8 TB.

Because codec generation drives bitrate. A Hikvision 4K H.265+ records at ~8 Mbps; an older H.264 4K at ~16 Mbps; an Axis Zipstream 4K at ~5 Mbps for equivalent quality. Same scene, same resolution, three different storage answers. The calculator carries the manufacturer-stated recording-stream bitrate for each camera profile and lets you override if your install measures differently.

Surveillance-rated drives in 8 / 10 / 16 TB sizes. 8 TB is the commodity sweet spot (best capacity-per-drive value). 16 TB makes sense for NVRs with limited bay count. The calculator shows the HDD count for each size; the right choice depends on the NVR's drive-bay count and the operational policy (RAID-1, RAID-5, RAID-6 affects usable capacity vs raw).

It includes headroom for filesystem and OS overhead, and the drive plan it prints is RAW capacity. It does not model RAID parity, and a flat percentage cannot, because the cost depends on how many drives are in the array. Parity consumes 1/n of raw capacity on RAID-5 and 2/n on RAID-6, where n is the drive count — so a six-drive RAID-5 gives up 17% of what you buy and a four-drive RAID-5 gives up 25%. Read the other way round, which is the way you size: to hold U usable you must buy raw = U × n/(n−1) on RAID-5 and U × n/(n−2) on RAID-6 — an uplift of 20% over usable at six drives, 33% at four, and 100% for a four-drive RAID-6. The smaller the array, the more parity costs. Take the tool's figure as the usable capacity you need and size the array on top of it. Formatted capacity is a further reduction, because drives are sold in decimal TB and reported by the operating system in binary TiB, which is about 9% less.

No. It is a sizing tool for the storage layer of an early-stage brief. It does not specify the NVR model, the licensing plan, the structured-cabling backbone, the network architecture (VLAN segmentation, switch sizing, multicast handling) or the cyber-security posture. Those are the design conversation. The calculator's outputs are the brief; the design is what follows.