How much storage for 30 days?
10.37 TB for 8 cameras at 4 Mbps each.
Enter these values
Choose Required capacity, target 30 days and 24 hours/day. Enter 8 cameras and 4 Mbps in group 1; select Calculate estimate.
Planning guide
NVR storage calculator
Estimate the capacity you need, or the recording days your drive can hold. Start with average camera bitrates, daily recording hours and capacity available for video.
This NVR planner also serves as a security camera storage calculator for CCTV recording: use the same camera counts, average recorded bitrates and recording schedule to estimate capacity or recording days.
The estimate uses video bitrate rather than a specific codec. It does not confirm DVR compatibility, supported recording formats or drive support; check those limits on your recorder.
Updated
Capacity or recording days
Group cameras by measured or configured average bitrate. Resolution alone is not a bitrate.
Three plans you can check in the calculator
These examples use assumed average bitrates and 24 recording hours/day. They estimate video payload in decimal TB, before audio, overhead and reserve space.
How long does 4 TB hold?
11.57 days for the same 8 cameras, with 4 TB usable for video.
Enter these values
Choose Recording days from capacity. Enter 4 TB usable for video and 24 hours/day, with 8 cameras at 4 Mbps. Use the space available for video, rather than assuming the drive label is all usable.
What if the bitrates differ?
3.02 TB for 4 cameras at 4 Mbps plus 2 at 2 Mbps, over 14 days.
Enter these values
Choose Required capacity, target 14 days and 24 hours/day. Enter 4 cameras at 4 Mbps, then Add camera group with 2 cameras at 2 Mbps. Calculate the estimate; both groups share the same schedule.
Use measured average bitrates when available. Changing resolution or codec does not set a universal bitrate. For event recording, use measured recorded hours including pre/post-event clips.
Assumptions and worked examples
The result estimates video data, not a promised retention period. Use average bitrates from the intended recording settings and drive space available for video. All camera groups in one calculation share the same daily recording hours; calculate separate schedules separately.
How the estimate works
Both modes estimate video payload, not guaranteed retention. For groups sharing a daily schedule:
Video TB = sum(cameras × average Mbps) × hours/day × days × 0.00045
Recording days = TB usable for video ÷ [sum(cameras × average Mbps) × hours/day × 0.00045]
At 24 hours/day, use 0.0108 instead of hours/day × 0.00045. Units are decimal: 1 Mbps = 1,000,000 bits/second; 8 bits = 1 byte; 1 TB = 1,000,000,000,000 bytes. A drive labelled 4 TB is not necessarily 4 TB available for video.
Check the worked examples
- Capacity: 8 cameras × 4 Mbps × 30 days × 0.0108 = 10.368 TB, displayed as 10.37 TB. At 2 Mbps each, the same schedule gives 5.184 TB.
- Mixed groups: 4 cameras × 4 Mbps plus 2 cameras × 2 Mbps = 20 Mbps. Over 14 continuous days, the groups use 2.4192 TB + 0.6048 TB = 3.024 TB.
- Recording days: 4 cameras × 4 Mbps × 0.0108 = 0.1728 TB/day. A 4.00 TB allocation for video holds about 23.15 days under these assumptions.
These are calculations, not customer cases. Add full-precision values and round only the final display. All groups in one calculation share daily hours; calculate different schedules separately. Zero recording load does not produce a meaningful finite retention estimate.
Allow for the recorder and real scene
Allow for audio, filesystem/database overhead, reserved space, stored exports and growth before choosing drives. Check supported drive models, bays, capacity limits and redundancy separately; compare decimal TB with the recorder's reported units.
Why adding 20% differs from reserving 20%
Adding 20% to a 3.024 TB payload gives 3.6288 TB. Leaving 20% of total capacity unused requires 3.024 ÷ 0.8 = 3.78 TB. Neither is a universal manufacturer requirement; state the allowance and why it applies.
Bitrate, compression and event-recording assumptions
Measure representative busy and nighttime operation. A configured bitrate ceiling may differ from the average. Axis describes bitrate-control differences; confirm the settings available on your models. Do not apply another H.265 discount to a bitrate that already reflects compression.
Event duration depends on activity, sensitivity and pre/post-event buffers. Compare a measured scenario with continuous recording; do not promise a fixed saving. Recheck after settings or activity change.
Verify after installation
Keep models, firmware, drive configuration and recording settings with measured stored data. Check each stream, playback and export. Once enough time has passed, compare the oldest usable recording with the target. A 24-hour sample can refine a forecast; it cannot prove 30-day retention.
Request a storage review with grouped camera counts, measured or assumed bitrate, schedule, target days, audio needs and existing models. Check NVR options and prepare the recording handover.
Drive and retention checks
Resolution does not fix bitrate or recording days. Measure the selected codec, frame rate and scene; H.265 savings vary with equipment and settings. For mixed resolutions, calculate each bitrate group and add the totals. Estimate event recording from measured recording hours, including pre-event and post-event clips, rather than assuming a fixed percentage saving.
Choose a drive the recorder actually supports
- Check the exact NVR drive list, drive interface, bay count, maximum capacity per bay and total supported capacity.
- Use a drive suitable for the intended continuous recording workload; confirm supported models, firmware and cooling requirements.
- Separate labeled capacity from usable video space. Allow for audio, filesystem overhead, reserved space and growth.
- If RAID is supported, calculate usable capacity for the selected mode. RAID does not replace an independent copy for equipment theft or loss.
Verify the recording window after installation
Set retention from when incidents are discovered and reviewed: a weekend delivery dispute may need footage before Monday. Check overwrite settings and timestamps, then retrieve and export the oldest required interval after enough days have elapsed. Verify recording across all channels during busy activity; a live image does not prove retention.
Reducing frame rate, changing codec or using event recording changes the evidence available. Test moving-subject detail and event coverage before using those changes to meet a capacity target. Review the recording-mode guide and codec comparison.