How Much Storage Does a CCTV System Need?

“How big a hard drive do I need?” is one of the most common CCTV questions, and the honest answer is: it depends on how much video your cameras produce. The good news is that the maths is simple once you know the bitrate. This guide shows you how to estimate it and how to choose between microSD cards, hard drives and cloud storage.

The simple formula

Every camera streams video at a certain bitrate, measured in megabits per second (Mbps). Storage depends on three things:

Storage = bitrate × hours recorded per day × number of days

Because there are 8 bits in a byte, one camera recording at 1 Mbps for 24 hours uses about 10.8 GB per day (1 × 3,600 seconds × 24 hours ÷ 8 = 10,800 MB). From there it is multiplication:

• GB per day per camera ≈ bitrate in Mbps × 10.8 (for 24-hour recording)
• Total ≈ GB per day × number of cameras × days you want to keep

Two worked examples

• 4 cameras, 2MP, H.265, about 1.5 Mbps each: 1.5 × 10.8 = 16.2 GB per camera per day, or about 65 GB a day for all four. Thirty days needs roughly 1.9 TB, so a 2TB drive gives you about a month.
• 8 cameras, 4MP, H.265, about 3 Mbps each: 3 × 10.8 = 32.4 GB per camera per day, or about 260 GB a day. Thirty days needs roughly 7.8 TB, so plan for an 8TB drive or two 4TB drives.

These are estimates. Drive makers count 1 TB as 1,000 GB, and real bitrates move up and down with the scene, so leave some headroom.

What affects the bitrate?

• Resolution: 4MP and 4K cameras produce more data than 2MP.
• Frame rate: 25 frames per second looks smoother but uses more space than 12 or 15, which is plenty for most security footage.
• Compression: H.265 needs much less space than H.264 for similar quality.
• Scene activity: busy roads, swaying trees, rain and low-light noise push the bitrate up.
• Bitrate mode: constant bitrate (CBR) is predictable, while variable bitrate (VBR) saves space on quiet scenes.

H.265 vs H.264

H.264 has been the standard for years and works with almost everything. H.265 (also called HEVC) was designed to deliver similar picture quality at roughly half the bitrate, and in CCTV it usually brings a big saving, although the exact figure varies with the scene and the camera. Many brands also offer “smart” versions such as H.265+ that squeeze static scenes even further.

If your cameras and recorder both support H.265, use it. Just check that any older viewing software or PCs you use for playback can handle it.

Typical bitrates (approximate)

Camera	H.264	H.265	H.265 per camera per day (24h)
2MP (1080p)	about 2 to 4 Mbps	about 1 to 2 Mbps	about 11 to 22 GB
4MP	about 4 to 8 Mbps	about 2 to 4 Mbps	about 22 to 43 GB

Treat these as rough ranges, not specifications. Your recorder shows the actual bitrate of each camera in its settings, and that is the number to use.

Continuous or motion recording?

Continuous recording keeps everything, which helps when you need to see what happened just before an event. Motion or event recording saves a lot of space on quiet cameras but can miss context. A common approach is continuous recording on key cameras such as the gate, with motion recording on quieter ones.

microSD vs hard drive vs cloud

microSD cards

Used in Wi-Fi cameras. Check the maximum card size your camera supports and choose a high-endurance card made for constant recording. Remember that if a camera is stolen, its card goes with it.

Hard drives in a DVR or NVR

The best choice for multi-camera systems. Surveillance-grade drives such as WD Purple or Seagate SkyHawk are built for recording around the clock. Larger NVRs take two or more drives for extra capacity.

Cloud storage

Brand plans such as EZVIZ CloudPlay or Tapo Care keep event clips off-site, so footage survives even if the camera is damaged or stolen. They are usually priced per camera and rely on your upload speed, so they work best as a backup for your most important views.

Local tips

• Put the recorder on a UPS. Sudden power cuts can corrupt recordings and shorten drive life.
• Keep the recorder somewhere cool and ventilated, away from damp.
• After an outage, check that the recorder is recording again and that the time is correct.

Frequently asked questions

What happens when the hard drive is full?

Most recorders overwrite the oldest footage automatically, so the system keeps running and always holds the most recent days. Check that overwrite is switched on in the storage settings.

How many days of recording should I keep?

For most homes, two to four weeks is enough to notice and review an incident. Businesses may choose longer based on their own policies or insurer advice, and should only keep footage as long as they need it.

Can I add a bigger drive later?

Usually, yes. Check the recorder’s maximum supported capacity and the number of drive bays. Installing a new drive requires formatting it, so export any footage you need first.

Want exact numbers for your cameras? Try the storage calculator on our CCTV and security services page: enter your cameras, resolution and days of recording to see the drive size you need. For help choosing a recorder or drive, call our Kandy team on +94 72 299 9915 or email info@eudora.lk.

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