Calculator
Formula Used
Adjusted bitrate = Base bitrate × Codec factor × Scene factor × Recording activity × Audio factor.
Daily storage GB = Cameras × Adjusted bitrate Mbps × Recording hours × 3600 ÷ 8 ÷ 1000.
Base storage TB = Daily storage GB × Retention days ÷ 1000.
Recommended TB = Base storage TB × Spare capacity factor × Recorder overhead factor.
This calculator uses decimal terabytes. Your recorder or computer may display capacity in binary units.
How to Use This Calculator
- Enter the number of cameras connected to the recorder.
- Select a resolution profile and enter the expected frame rate.
- Enter the average bitrate for each camera stream.
- Choose the codec and scene complexity that best match the site.
- Set recording hours, retention days, and activity percentage.
- Add overhead for audio, spare capacity, and recorder storage rules.
- Press the calculate button to view the recommended drive size.
- Use the CSV or PDF button to save the result.
Example Data Table
| Site Type | Cameras | Mbps Per Camera | Hours Per Day | Retention | Codec | Suggested Capacity |
|---|---|---|---|---|---|---|
| Small shop | 4 | 2 | 24 | 14 | H.265 | 0.87 TB |
| Home system | 6 | 3 | 18 | 21 | H.264 | 2.76 TB |
| Warehouse | 16 | 5 | 24 | 30 | H.265 | 19.44 TB |
| Parking area | 24 | 6 | 24 | 45 | H.264 | 90.98 TB |
Security Camera Hard Drive Planning Guide
Why storage planning matters
A security system is only useful when footage is available at the right moment. A small drive may overwrite evidence before anyone notices a problem. A very large drive can waste budget that could improve cameras, lighting, or backup power. Good planning starts with the video bitrate, because bitrate describes how much data each camera creates every second. The number also changes with resolution, frame rate, codec, motion, and scene detail. A busy entrance usually needs more space than a quiet hallway.
Main factors to review
The calculator separates each factor so the estimate is easier to audit. Camera count scales storage directly. Recording hours define whether the system records all day or only during active periods. Retention days set the required archive length. Codec efficiency adjusts the base bitrate for common recording formats. Scene complexity adds room for trees, rain, crowds, traffic, or low light noise. Audio overhead covers microphones when they are recorded with the stream. Spare capacity keeps the drive from running near full, which helps future growth and routine file handling.
Using the result wisely
The recommended capacity is a planning number, not a contract guarantee. Real recorders may store metadata, snapshots, logs, and system files. Some devices also reserve space for indexing or health checks. Drive makers often use decimal terabytes, while operating systems may display tebibytes. This difference can make a new drive look smaller than expected. For important sites, choose surveillance rated drives, use a recorder with health alerts, and test the actual retention after installation. Review the estimate again after changing cameras, frame rate, compression, or detection rules.
Practical buying advice
When the required capacity falls between common drive sizes, round upward. A small safety margin is cheaper than losing a critical day of footage. For multi drive recorders, account for mirror or parity overhead before buying. Also consider replacement access. A site that needs continuous evidence should avoid relying on one aging disk. Keep firmware updated, label drives, and document the final settings. This makes future troubleshooting faster and prevents accidental retention loss. Store screenshots of key configuration pages with the maintenance file for reference. Check retention regularly after busy weeks.
FAQs
What bitrate should I use?
Use the actual bitrate shown in your recorder or camera settings. If unsure, start with 2 Mbps for basic 1080p video and increase it for higher resolution, more motion, or sharper detail.
Does H.265 always use less storage?
Usually yes, but results depend on camera quality and scene conditions. H.265 can reduce storage compared with H.264, especially when the recorder and cameras handle compression well.
Why add spare capacity?
Spare capacity gives room for bitrate spikes, recorder files, future cameras, and display differences between decimal and binary storage. It also avoids planning too close to the limit.
What is recording activity percent?
It estimates how often video is recorded. Use 100 percent for continuous recording. Use a lower number for motion based recording when the camera records only during activity.
Can I use this for NVR and DVR systems?
Yes. The storage math works for both. Enter the bitrate per camera, recording hours, and retention days that match your recorder settings.
Why does my drive show less space?
Drive labels often use decimal terabytes. Many systems display binary units. Recorders may also reserve space for indexes, logs, snapshots, and system data.
Should I use surveillance rated drives?
Surveillance rated drives are designed for constant video writing. They are a better choice for recorders that run every day and store important evidence.
How often should I recalculate storage?
Recalculate after adding cameras, changing resolution, raising frame rate, changing codec, enabling audio, or adjusting motion detection. Small setting changes can affect retention.