Example Data Table
| Scenario | Cameras | Mode | Resolution | Codec | Days | Approx. Storage |
|---|---|---|---|---|---|---|
| Small retail | 8 | Continuous | 1080p @ 20fps | H.265 | 14 | ~2.5 TB |
| Warehouse | 24 | Motion 25% | 4MP @ 15fps | H.265 | 30 | ~6.0 TB |
| Office campus | 64 | Continuous | 4K @ 20fps | H.265+ | 30 | ~55 TB |
Formula Used
- Per-camera bitrate (Mbps) is auto-estimated from presets, or set manually.
- Total bitrate (Mbps) = cameras × (video Mbps + optional audio Mbps).
- Effective hours/day = hours/day × duty cycle (motion % if selected).
- Raw bytes = total Mbps × 1,000,000 ÷ 8 × seconds recorded.
- With overhead = raw × (1 + overhead%).
- Final = with overhead × (1 + safety margin%).
- Drive count = ceil(final ÷ (drive capacity × usable factor)).
How to Use This Calculator
- Enter camera count, retention days, and recording hours.
- Choose continuous or motion recording mode.
- If using motion, set expected activity percentage.
- Select codec, resolution, fps, and quality profile.
- Optionally type a custom bitrate per camera.
- Add overhead and safety margin for real-world buffers.
- Pick unit style and drive size for capacity planning.
- Press Calculate to view results above the form.
- Use CSV or PDF to share the estimate with others.
Capture requirements and compliance targets
Start by defining who will review footage and why. Retail loss prevention often needs 14–30 days, while safety and industrial sites may require 60–90 days. Document camera purpose, required identification distance, and any policy or legal retention rules. Clear requirements prevent undersized drives and costly mid-project changes.
Bitrate is the real driver of storage
Storage scales with total bitrate and recording duration, not just resolution. Two 1080p cameras can consume more space than one 4K camera if the first pair runs higher fps, higher quality, or complex scenes. Use a measured encoder bitrate when available, or apply conservative planning values for busy entrances and outdoor motion. If bandwidth is limited, reduce fps before dropping resolution for better detail per bit.
Use motion recording carefully
Event recording can cut storage dramatically, but only if motion rules are tuned. High sensitivity, shadows, rain, and headlights can raise duty cycle beyond expectations. Treat motion percentage as an average of real activity, then add a safety margin. For critical zones, consider continuous or pre/post event buffers.
Account for overhead, redundancy, and usable capacity
DVR/NVR systems store indexes, metadata, and file containers that add overhead. Arrays also reduce usable space through mirroring or parity. Plan with an overhead allowance and a usable-capacity factor, and keep steady utilization below about 80% to protect performance and extend drive life. Choose surveillance-rated drives for 24/7 workloads. Prefer modern codecs when supported, but confirm playback compatibility across monitors and mobile apps.
Validate with field tests before final purchase
Run a short pilot using the intended codec, fps, and quality settings. Export a VMS or recorder report showing actual Mbps per camera during day and night. Multiply the measured bitrate by retention days to confirm capacity, then adjust margin for seasonal changes, additional cameras, or higher scene activity. Keep notes on lens angle changes, WDR, and noise reduction, because these settings can materially shift bitrate for internal auditability, future forecasting.
FAQs
How accurate are storage estimates without a measured bitrate?
They are planning-grade. Presets assume typical scenes and encoder settings. For best accuracy, pull the recorder’s actual Mbps per channel during day and night, then re-run the calculator using the custom bitrate field.
Should I choose decimal TB or binary TiB?
Drive labels use decimal TB, but many systems display binary TiB. Pick decimal for purchasing decisions, and binary to match what an operating system reports. The difference is normal and does not mean capacity is missing.
What motion percentage should I use?
Use an average duty cycle after tuning motion rules. Busy entrances may exceed 50%, while quiet corridors can be under 10%. If unsure, start with 30% and apply a stronger safety margin until real data is available.
Why add overhead and safety margin?
Overhead covers indexes, metadata, and file containers. Safety margin covers scene complexity, seasonal changes, and future cameras. Together they reduce the risk of falling short of required retention.
How many drives should I plan for with redundancy?
Select a usable factor that reflects your layout. Mirroring often halves usable space, while parity reduces it less. This calculator then converts final storage into a rounded drive count based on that usable capacity.
What settings reduce storage while keeping useful evidence?
Lower fps first, then adjust quality. Consider a more efficient codec when supported. Use motion recording in low-risk areas, and keep continuous recording for critical zones that require complete timelines.