How Much Storage Do Security Cameras Need?

The storage formula

For a continuously recorded stream:

Storage (GB) ≈ bitrate (Mbps) × 10.8 × cameras × days.

The constant comes from converting megabits per second into bytes over 86,400 seconds in a day. It is a planning approximation using decimal gigabytes.

Example: four cameras averaging 4 Mbps for 30 days:

4 × 10.8 × 4 × 30 ≈ 5,184 GB, or about 5.2 TB of video before adding safety margin and filesystem/other usage.

Continuous recording storage per camera

These values are for one camera recording all day at the stated average bitrate. Variable-bitrate cameras can rise sharply in busy or noisy scenes, so size storage from measured behavior when possible.

Why resolution alone cannot tell you storage size

A 4K camera does not consume one fixed number of gigabytes. Two 4K cameras can use very different bitrates because of:

• H.264 vs H.265 codec;
• frame rate;
• quality/compression setting;
• constant vs variable bitrate;
• scene complexity, noise, rain, leaves and traffic;
• whether audio is recorded;
• manufacturer encoding behavior.

Use the bitrate reported/configured by the camera or measure the actual recording files. Resolution is important for image detail, but bitrate is the direct storage input.

How much storage for 4 security cameras?

At an average 4 Mbps per camera, four continuous cameras use about 172.8 GB/day. Approximate video storage would be:

• 7 days: 1.21 TB
• 14 days: 2.42 TB
• 30 days: 5.18 TB

A nominal 6 TB drive may therefore be a reasonable starting capacity for that simplified 30-day example, but do not treat nominal capacity as fully usable. Leave room for formatting, system files, bitrate variation and operational headroom.

How much storage for 8 security cameras?

At the same 4 Mbps average, eight continuous cameras use about 345.6 GB/day:

• 7 days: 2.42 TB
• 14 days: 4.84 TB
• 30 days: 10.37 TB

This is why camera count and retention should be planned together. Doubling the camera count approximately doubles storage use when everything else stays equal.

How motion recording changes the calculation

If recording is event-triggered, multiply the continuous estimate by the approximate recording duty cycle. A camera that records 20% of the time may use around 20% of the continuous space at the same bitrate.

But do not assume a duty cycle before testing. A view with moving trees, street traffic, insects at night or poor motion tuning can record for most of the day. Measure several normal days before buying storage for a long retention target.

How scheduled recording changes the calculation

If you record 12 hours per day instead of 24, the time-based portion of the estimate is roughly halved. For a small office that only needs after-hours coverage, scheduling can reduce storage without lowering image quality.

Schedules also make retention more predictable than motion-only recording in scenes where activity varies widely.

Should you record the main stream or substream?

For evidence, the main stream normally provides the useful detail. A substream is often designed for low-bandwidth live viewing and may have lower resolution, frame rate or bitrate. Recording only the substream saves space but can reduce the detail available when you zoom into an incident later.

A common design is to record the main stream locally and use a lower-bitrate stream for remote live view.

How much free space should you leave?

Do not plan to consume every advertised gigabyte. The recording drive needs operational headroom, and Windows needs free space for updates, logs and temporary files. If recordings share the system drive, be even more conservative.

For an important multi-camera installation, consider a dedicated recording drive so normal Windows/app activity does not compete with surveillance files.

Measure your actual Security Eye storage use

1. Configure the cameras at the resolution, frame rate and recording mode you intend to keep.
2. Run Security Eye for a representative 24-hour period.
3. Measure how much the recording folder grew.
4. Repeat on a busy day and, for outdoor cameras, a night with normal lighting/weather.
5. Use the higher realistic daily figure for capacity planning.
6. Multiply by your target retention days and add headroom.

This real measurement automatically captures the effect of your actual codecs, motion activity and camera settings, so it is more reliable than a generic “1080p needs X GB” chart.

Storage planning checklist

• Know the number of cameras.
• Know the average main-stream bitrate or measure actual file growth.
• Choose continuous, scheduled or event recording deliberately.
• Define the retention target in days.
• Add spare capacity for bitrate peaks and operational headroom.
• Decide how important clips will be exported or backed up.
• Review storage after adding cameras or raising video quality.