H.265 and CCTV Storage: How Many Days Will Your Hard Disk Record?

“How many days will it record?” is one of the most common CCTV questions. The answer depends on a few numbers you can control. Once you understand them, you can size a hard disk properly instead of guessing.

The four things that decide storage

1. Bitrate: how much data each camera sends per second (for example 2 Mbps or 4 Mbps). This is the biggest factor.
2. Number of cameras.
3. Recording hours: 24 hours continuous, or only when motion is detected.
4. Days you need to keep.

Resolution, frame rate and scene activity all change the bitrate. A busy road at 25 fps needs much more than a quiet corridor at 12 fps.

What H.265 changes

H.265 (HEVC) is a newer compression standard than H.264. It is designed to deliver similar picture quality at a much lower bitrate. Manufacturers also add their own “smart” versions (such as H.265+) that cut bitrate further on quiet scenes.

In practice, switching cameras and recorder to H.265 often lets the same hard disk keep noticeably more days of footage. The saving depends on the scene, so always check the real result after a few days.

A simple estimate

Storage per day (GB) is roughly: bitrate in Mbps × 10.8 × hours ÷ 24 for each camera. For example, a 2 Mbps camera recording 24 hours uses about 21.6 GB per day. Eight such cameras for 30 days need about 5.2 TB.

Rather than doing this by hand, use our free CCTV Storage Calculator. Enter your cameras, resolution and codec, and it suggests a suitable hard disk size.

Ways to keep more days

• Use H.265 or smart codec settings.
• Lower frame rate on indoor or quiet cameras (12 to 15 fps is often enough).
• Use motion or event recording on low-priority cameras.
• Use surveillance-grade hard drives, which are built for constant writing.