CCTV Storage Calculator
Estimate how much hard drive space your surveillance system needs based on camera count, bitrate, recording hours, and retention period.
Why a CCTV storage calculator matters
Storage is one of the biggest hidden costs in any surveillance deployment. Many people focus on buying cameras, but quickly discover that hard drives, recording servers, and retention requirements drive long-term budget. A good CCTV storage estimate helps you avoid two expensive mistakes:
- Under-sizing: running out of space and losing critical footage before your required retention window.
- Over-sizing: buying more disks and NVR capacity than you actually need.
How CCTV storage is calculated
The core inputs are straightforward: number of cameras, average bitrate, recording schedule, and number of days you want to keep footage. This calculator uses the common industry formula:
After that baseline number, we apply overhead and safety margin so your final estimate is practical for real-world operations.
Input breakdown
- Number of cameras: total streams being recorded continuously or by schedule.
- Bitrate per camera: average data rate, usually measured in Mbps.
- Recording hours/day: 24 for always-on recording, lower for motion/event recording.
- Retention days: how long footage must be stored (policy, legal, or operational requirement).
- Overhead: extra capacity consumed by system-level activity and formatting.
- Safety margin: recommended reserve for unusual activity and growth.
Typical bitrate ranges you can start with
These are rough planning values only. Your exact result depends on scene complexity, lighting, and codec settings.
- 1080p H.265: ~1.5 to 3 Mbps
- 1080p H.264: ~3 to 6 Mbps
- 4MP H.265: ~2.5 to 5 Mbps
- 4K H.265: ~6 to 12 Mbps
- 4K H.264: ~10 to 20+ Mbps
Example scenario
Suppose you have 16 cameras at 4 Mbps each, recording 24/7, and need 45 days of retention. Add 15% overhead and a 10% safety margin.
- Raw storage for footage: approximately 15.2 TB
- After overhead: approximately 17.5 TB
- After safety margin: approximately 19.3 TB
In this example, planning for at least 20 TB usable capacity is a reasonable starting point.
Practical deployment notes
1) NVR/DVR usable space is not raw disk size
If you use RAID, parity and redundancy reduce usable capacity. Always calculate on usable space, not marketed drive totals.
2) Motion scenes can spike bitrate
Parking lots, entrances, and busy streets create bursts in storage consumption. That is why a safety margin is strongly recommended.
3) Retention policies differ by industry
Retail, healthcare, logistics, and critical infrastructure often have different minimum retention requirements. Confirm policy and compliance requirements before final hardware purchases.
Ways to reduce CCTV storage without losing evidence quality
- Switch from H.264 to H.265 when supported.
- Use variable bitrate (VBR) with quality limits instead of fixed bitrate in many environments.
- Apply motion recording schedules on low-risk cameras.
- Reduce frame rate where full motion detail is unnecessary (for example, from 30 fps to 15 fps).
- Tune stream settings by camera role (entry points vs. hallways vs. overview cameras).
Final thought
A CCTV storage calculator gives you a strong first-pass estimate for budget and system design. For final procurement, verify your assumptions with a short pilot recording period and real bitrate measurements from your exact camera models.