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CCTV Storage Calculator — How Much Hard Disk Do You Need?

A simple formula to calculate the right CCTV hard-disk size based on number of cameras, resolution and how many days of footage you need.

8 January 2026
Chaukanna Team
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CCTV Storage Calculator — How Much Hard Disk Do You Need?

Buying a CCTV system without sizing the hard disk correctly is the most expensive mistake we see in Pune homes and offices. Too small a disk and your footage overwrites before you realise a theft happened. Too large and you spend money you didn’t need to.

Here is the simple formula and a quick reference table.

The formula


HDD (in GB) = cameras × bitrate (Mbps) × 0.45 × hours × days


The 0.45 converts Mbps × hours into roughly GB at H.264. For H.265 (modern recorders), divide by 2.

Typical bitrates

| Resolution | Main stream bitrate |
|---|---|
| 2MP (1080p) | 2–3 Mbps |
| 4MP | 4–6 Mbps |
| 5MP | 5–7 Mbps |
| 8MP / 4K | 8–12 Mbps |

H.265 cuts these roughly in half. Most modern Hikvision, CP Plus and Dahua DVR/NVRs use H.265+.

Quick reference table (24×7 recording, H.265)

| Cameras | Resolution | 30 days | 60 days | 90 days |
|---|---|---|---|---|
| 4 | 2MP | 1 TB | 2 TB | 3 TB |
| 4 | 4MP | 2 TB | 4 TB | 6 TB |
| 8 | 2MP | 2 TB | 4 TB | 6 TB |
| 8 | 4MP | 4 TB | 8 TB | 12 TB |
| 16 | 2MP | 4 TB | 8 TB | 12 TB |
| 16 | 4MP | 8 TB | 12 TB | — split into multiple HDDs |
| 24 | 4MP IP | 12 TB | — | — split into multiple HDDs |

How many days should you keep?

- Home: 15–30 days is plenty
- Shop: 30 days minimum (shrinkage takes time to discover)
- Office: 30 days for compliance comfort
- Society: 30 days minimum, 45–60 days preferred
- Bank / jewellery / pharmacy: 90 days (often mandatory)

Tips to make storage last longer

- Use H.265+ codec on the recorder (saves ~50% vs H.264)
- Set motion-triggered higher bitrate, idle lower bitrate on indoor cameras
- Use 2 streams — main for recording, sub for mobile viewing
- Avoid 4K on cameras that don't need it (shop floor, godown)

Surveillance hard disks — buy the right kind

Don’t use desktop / laptop HDDs in DVRs. They burn out in 6–12 months because surveillance is 24×7 write-heavy.

Use:
- WD Purple — most common, reliable
- Seagate SkyHawk — equally good
- Toshiba S300 — good budget option

Avoid: WD Blue / Green, Seagate Barracuda — these are for desktops, not DVRs.

Want help sizing?

Tell us your camera count, resolution and target retention days on WhatsApp and we’ll size the HDD for you in 2 minutes.

FAQs

Q: Can I add a second hard disk later?
A: Most 8-channel and above DVR/NVRs have 2 SATA slots. We can add a second HDD later.

Q: What happens when the HDD fills up?
A: It loops — overwrites the oldest footage first.

Q: Is cloud backup worth it?
A: For most homes and shops, no. For high-value sites (jewellery, pharma, finance), yes — cloud for the last 30 days as backup.

Tags

#CCTV storage#CCTV hard disk#CCTV retention days

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