How to Calculate How Much CCTV Storage You Need: A Complete Guide Homes and Businesses

One of the most common questions we hear from customers planning a new security camera installation is: “How many days of footage will my system actually keep?” It’s a critical question and one that too many people only think about after their system is already installed.

Get it wrong, and you could find that your CCTV system has overwritten last week’s footage of a break-in before you even knew it happened. Or you might overspend on enterprise-grade storage you’ll never come close to filling.

In this guide, we’ll walk you through exactly how CCTV storage works, the factors that determine how much you need, and how to calculate the right amount for your home or business.

Why CCTV Storage Retention Matters

Storage retention refers to the number of days your security system keeps recorded footage before it’s automatically overwritten by newer recordings. Most NVR (Network Video Recorder) or VMS (Video Management System) use a loop recording method and once the hard drive is full, the oldest footage is deleted first to make room for new recordings.

This means if your system only retains 7 days of footage and you’re away on a two-week holiday, you could return to find the evidence of an incident has already been erased. For businesses, particularly those in retail, hospitality or warehousing, inadequate retention can create serious compliance and liability issues.

The Five Factors That Determine Your Storage Needs

Before you can calculate your storage requirements, you need to understand the five key variables that affect how much space your CCTV system will consume.

1. Camera Resolution

Resolution is a big driver of storage consumption. Higher resolution cameras capture more detail which is exactly what you want when trying to identify a face or a numberplate but they also produce significantly larger files.

For example jumping from a 1080p camera to a 4K camera can roughly triple your daily storage consumption per camera.

2. Frame Rate (Frames Per Second)

Frame rate determines how smooth the recorded video appears. A higher frame rate captures more individual frames each second, which is useful for fast-moving scenes such as traffic or shopfronts but it also increases storage usage in direct proportion.

• 15 fps is the most common setting for general surveillance and provides a good balance between smooth footage and manageable file sizes.
• 30 fps provides real-time video but doubles the storage requirement compared to 15 fps.

For most residential and small business applications, 15 fps is more than adequate. You can always increase the frame rate on specific cameras covering high-priority areas without applying it across the entire system.

3. Video Compression (Codec)

The compression codec your NVR and cameras use has an enormous impact on storage efficiency. Modern compression technology can dramatically reduce file sizes without noticeably affecting image quality.

• H.264 is the older standard still used in many systems. It’s widely compatible but produces larger files.
• H.265 (HEVC) is the current standard for most professional-grade systems and typically reduces storage requirements by 30–50% compared to H.264 at the same quality level.
• H.265+ (also called Smart Compression or Smart Codec) takes this further by dynamically adjusting compression based on scene activity and allocating more data to moving objects and less to static backgrounds. This can achieve 50–80% savings over standard H.264.

4. Number of Cameras

This one is straightforward, the more cameras you have, the more storage you’ll need. Each camera generates its own continuous data stream, and these all add up on the same hard drive or drives inside your NVR or VMS Server.

A typical home security setup might include 4–8 cameras, while a business premises could easily require 16, 32, or more. When planning storage, you need to account for every camera in the system.

5. Recording Mode

How your cameras are configured to record makes a significant difference to storage consumption:

• 24/7 continuous recording captures everything around the clock, providing complete coverage with no gaps. This is the most storage-intensive mode but ensures you never miss an incident.
• Motion-triggered recording only saves footage when the camera detects movement. This can reduce storage usage by 50–70% depending on the scene, but it does carry a small risk of missing events outside the detection zone.
• Scheduled recording allows you to define specific hours for recording. For example, after business hours only. This can dramatically reduce storage for commercial sites that are occupied during the day.

Many modern systems also support a dual-stream approach, where the NVR records continuously in a lower-resolution sub-stream and switches to high-resolution when motion detected.

The Storage Calculation Formula

Here’s the formula used by security professionals to estimate CCTV storage requirements:

Storage (GB) = Bitrate (Mbps) × 3600 × Hours × Days × Cameras ÷ 8 ÷ 1000

This looks more complicated than it is. Let’s break it down with a practical example.

Worked Example: A Typical Adelaide Home

Scenario: You’re installing 6 × 4MP cameras recording 24/7 for 30 days using H.265 compression at 15 fps.

• Bitrate per camera: approximately 3 Mbps (typical for 4MP at H.265, 15 fps, medium scene activity)
• Hours per day: 24
• Number of days: 30
• Number of cameras: 6

Calculation:

3 Mbps × 3,600 seconds × 24 hours = 259,200 Mb per camera per day

259,200 ÷ 8 = 32,400 MB per camera per day

32,400 ÷ 1,024 = approximately 31.6 GB per camera per day

31.6 GB × 6 cameras × 30 days = approximately 5,695 GB, or roughly 5.6 TB

In this scenario, you’d want a minimum of a 6 TB hard drive or ideally an 8 TB drive to allow buffer and any future camera additions.

Worked Example: A Small Business or Warehouse

Scenario: You’re installing 16 × 8MP (4K) cameras in a warehouse recording 24/7 for 30 days using H.265+ compression at 15 fps.

• Bitrate per camera: approximately 4 Mbps (H.265+ with smart compression reduces 4K bitrate significantly)
• Hours per day: 24
• Number of days: 30
• Number of cameras: 16

Calculation:

4 Mbps × 3,600 × 24 = 345,600 Mb per camera per day

345,600 ÷ 8 ÷ 1,024 = approximately 42.2 GB per camera per day

42.2 GB × 16 cameras × 30 days = approximately 20,250 GB, or roughly 19.8 TB

For a system of this size, you’d typically use an NVR or VMS with multiple hard drive bays, for example, 2 × 12 TB drives and ideally configure them in a RAID array for redundancy.

Quick Reference: Storage Estimates by Camera Count

The following estimates assume H.265 compression, 15 fps, continuous 24/7 recording, and medium scene activity. Actual figures will vary based on your specific configuration.

4 × 2MP (1080p) cameras:

• 7 days: approximately 440 GB
• 14 days: approximately 880 GB
• 30 days: approximately 1.9 TB

4 × 4MP cameras:

• 7 days: approximately 880 GB
• 14 days: approximately 1.8 TB
• 30 days: approximately 3.8 TB

8 × 4MP cameras:

• 7 days: approximately 1.8 TB
• 14 days: approximately 3.5 TB
• 30 days: approximately 7.5 TB

16 × 4K (8MP) cameras:

• 7 days: approximately 4.6 TB
• 14 days: approximately 9.2 TB
• 30 days: approximately 19.8 TB

How Many Days of Retention Do You Actually Need?

The right retention period depends on your circumstances and, in some cases, regulatory requirements.

Residential Properties

For most Adelaide homes, 14–30 days is a sensible target. This gives you enough time to notice an issue even if you’ve been away, review the footage, and report it to police. If you travel frequently or leave your property unattended for extended periods, aim for the higher end.

Businesses and Commercial Properties

30 days is widely considered the industry standard for Australian businesses, and aligns with the general recommendation from most state police services. However, some industries and licensing conditions may require longer:

• Licensed venues (pubs, clubs, bottle shops) in South Australia are often required to retain CCTV footage for a minimum of 30 days as a condition of their liquor licence and up to 90 days for late night.
• Retail businesses dealing with stock shrinkage or frequent shoplifting may benefit from 60–90 days of retention to identify patterns.
• Construction sites and high-value commercial premises may require 30–60 days depending on the nature of the site and insurance requirements.

Australian Privacy Considerations

Under the Australian Privacy Act 1988 and the Australian Privacy Principles, businesses are generally required to destroy personal information which includes identifiable CCTV footage and once it’s no longer needed for the purpose it was collected. In practice, this means retaining footage indefinitely “just in case” is not appropriate. A rolling 30–90 day retention cycle is considered best practice for most organisations.

Tips to Maximise Your Storage Without Sacrificing Quality

If your current system doesn’t hold as many days of footage as you’d like, there are several practical steps you can take before investing in larger hard drives.

Upgrade to H.265 or H.265+ compression. If your NVR and cameras support it but it hasn’t been enabled, switching from H.264 to H.265 can effectively double your retention overnight.

Use motion-triggered recording where appropriate. Cameras covering low-traffic areas such as a side gate or storage room can be set to record on motion only, saving significant storage without compromising coverage.

Adjust frame rates to match the scene. Not every camera needs 25 fps. A camera covering a quiet car park at night can run at 10 fps and still capture everything you need, while a camera over a shop entrance might stay at 15–25 fps.

Choose the right resolution for the job. A 4K camera isn’t always necessary. If a camera only needs to cover a small area like a doorway or till point, 2MP or 4MP may provide more than enough detail while using a fraction of the storage.

Choosing the Right Hard Drive for Surveillance

Standard desktop hard drives are not designed for the demands of 24/7 CCTV recording. Surveillance-grade drives, such as the Western Digital Purple or Seagate SkyHawk range are purpose-built for continuous writing, which is the primary workload of an NVR.

Key considerations when selecting a surveillance hard drive:

• Write-optimised firmware that prioritises continuous recording over read speeds.
• Vibration resistance to handle being installed alongside other drives in multi-bay servers.
• Workload ratings of 180 TB/year or higher, designed for always-on operation.
• Warranty most surveillance drives come with a 3-year manufacturer warranty.

For systems with 8 or more cameras, consider a NVR or VMS Server with multiple hard drive bays. This allows you to increase total capacity as needed and, if configured in a RAID setup, provides protection against data loss if a single drive fails.

When to Consider a CCTV Server Upgrade

If your current setup doesn’t support enough hard drive capacity to meet your retention requirements, or if it’s still running on H.264-only compression, it may be time to look at a system upgrade. Modern NVRs offer larger drive bays (many now support up to 40 TB or more across multiple bays), H.265+ compression, AI-powered smart recording features, and seamless smartphone monitoring.

An upgrade doesn’t necessarily mean replacing your cameras. Many modern NVRs are backwards-compatible with existing IP cameras, so you may only need to swap out the recorder itself.

Need Help Sizing Your CCTV Storage? Talk to Us

Every property is different, and the right storage configuration depends on your specific camera layout, resolution requirements, and how long you need to retain footage. Our team at Blu Sky Security Systems designs and installs CCTV systems across Adelaide every day , for everything from 4-camera home setups to multi-site commercial installations with 100+ cameras.

We’ll assess your property, recommend the right solution to meet your needs.

Request a free quote or call us on (08) 7123 4177 to discuss your CCTV storage requirements.