CCTV Hard Drive & Bandwidth Calculator

Planning a CCTV or IP video surveillance system requires accurate estimates of storage capacity and network bandwidth — two of the most critical and frequently underestimated factors in any security installation. Buy too little storage and footage gets overwritten before an incident is reviewed. Provision too little bandwidth and video streams lag, drop frames, or fail entirely during peak recording times. The CCTV Hard Drive & Bandwidth Calculator eliminates guesswork by computing both figures from a handful of straightforward inputs.

The core inputs are the bitrate per camera (in Megabits per second), the number of cameras, the daily recording hours, and the desired retention period in days. From these, the calculator derives total storage in both gigabytes and terabytes, total simultaneous bandwidth, and daily storage consumption — everything a system designer or IT administrator needs to specify hard drives and network switches.

Understanding bitrate is essential. Modern IP cameras encode video using H.264, H.265 (HEVC), or H.265+ compression codecs. A 2 MP (1080p) camera using H.264 typically streams at 2–6 Mbps depending on scene activity, quality settings, and frame rate. The same camera using H.265 might achieve comparable quality at 1–3 Mbps — roughly half the storage requirement. High-definition 4K cameras may need 8–25 Mbps per stream. Motion-based recording or variable bitrate (VBR) encoding can reduce average bitrate by 30–60% compared to constant bitrate (CBR), but for planning purposes using the peak CBR value is the conservative approach.

The formula underlying this calculator is straightforward: Storage (GB) = Bitrate (Mbps) × 3600 s/h × Hours/Day × Cameras × Days ÷ 8 ÷ 1000. Breaking this down: multiplying Mbps by 3600 converts to megabits per hour; multiplying by hours and cameras gives total megabits; dividing by 8 converts to megabytes; dividing by 1000 converts to gigabytes (using 1 GB = 1000 MB, the disk manufacturer standard).

Bandwidth is simply Bitrate × Number of Cameras — all cameras streaming simultaneously consume that much network capacity. A 16-camera system at 4 Mbps each requires 64 Mbps of network bandwidth on the surveillance LAN. This affects the choice of network switches (100 Mbps vs. Gigabit), the NVR's network interface, and storage server throughput.

When sizing NAS or NVR hard drives, always add a 15–20% overhead to the calculated figure. Drive manufacturers and file systems consume some space for metadata, parity data (if using RAID), and the file system itself. A calculated requirement of 10 TB becomes a practical requirement of 12 TB of raw drive capacity. For mission-critical installations, RAID-5 or RAID-6 configurations provide redundancy at the cost of additional drives.

Retention period requirements vary by application: retail environments typically keep 30–90 days of footage; financial institutions may require 90–180 days; critical infrastructure or government facilities sometimes mandate 365 days. Local regulations and insurance requirements may also specify minimum retention periods — always verify these before finalizing storage specifications.

This calculator is equally useful for both analog HD systems (HD-CVI, HD-TVI, AHD) connected to DVRs and IP camera systems connected to NVRs. The bitrate concept applies universally — enter the camera's configured or typical bitrate and the math is identical.