Quick answers
Continuous 24 h/day recording, decimal TB (1 TB = 1,000 GB). Open the NVR planner tab below for motion savings, safety buffer and drive recommendations.
Surveillance Storage Lab
Cameras & encoding
Schedule & retention
Drive recommendations (surveillance-rated drives)
| Drive size | Drives needed | Raw capacity |
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Retention sweep (same config)
| Retention | Storage needed |
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One lab, five surveillance calculators
This page is an NVR storage calculator and DVR storage calculator in one — a CCTV DVR storage calculator for analog/HD systems and a network-video planner for IP systems. The planner tab sizes storage for any network video recorder: enter camera count, resolution, fps, codec, recording schedule and retention days, and it returns total TB plus a drive recommendation. It works as an IP camera storage calculator and security camera storage calculator for any video surveillance storage calculator planning job, from a 4-camera home system to a 64-channel enterprise NVR.
Asking "how much storage do I need for 4 cameras 30 days"? Type 4 / 30 / 2 Mbps into the quick-answers box above — a typical 1080p H.265 setup needs about 2.59 TB. The recording-time tab inverts the math as a CCTV recording time calculator, NVR recording time calculator and CCTV DVR recording time calculator: it answers "how many days will 1TB record 4 cameras" (11.6 days at 2 Mbps each, 24 h/day) and "how much video can be stored on 1TB" from a single camera (1,111 hours at 2 Mbps).
Brand-specific planning is built in: the vendor tab is a Dahua storage calculator, Hikvision storage calculator and Axis storage calculator (plus Bosch, Hanwha, UniFi and Reolink) with typical per-resolution bitrates you can push straight into the planner. The codec tab is an H265 vs H264 storage calculator shown side-by-side for your exact setup, and the motion explorer quantifies motion detection storage savings — a motion detection storage savings calculator for cameras, schedules and retention you actually run.
For cameras with memory cards, the SD-card tab is a GoPro recording time calculator (4K/5.3K modes), dash cam recording time calculator and micro SD card recording time calculator — an SD card video storage calculator covering 32 GB to 1 TB cards. Finally, the retention presets and sweep table make it a CCTV retention calculator for 30-day (or 7, 14, 60 and 90-day) retention policies.
How the math works
- Core formula: TB = cameras × Mbps per camera × 3600 × hours/day × days × (1 − motion%) × (1 + buffer) ÷ 8 ÷ 1e12. Recording time is the inverse: hours = GB × 1e9 × 8 ÷ (total Mbps × 1e6) ÷ 3600.
- Bitrate estimate: Mbps = width × height × fps × bits-per-pixel ÷ 1e6, with typical bits-per-pixel of 0.08 (H.264), 0.056 (H.264+), 0.040 (H.265), 0.027 (H.265+) for average VBR scenes — e.g. 4MP (2688×1520) × 15 fps × H.265 ≈ 2.45 Mbps.
- Decimal TB: drive makers and most planners use 1 TB = 1,000 GB (1e12 bytes), so this tool does too — the numbers match what you buy.
- Typical, not exact: every preset is labeled typical. VBR recording swings with motion, lighting and noise; the 15% default safety buffer absorbs that. Sub-streams for live viewing add a little on top.
- Privacy: everything runs in your browser — no video, no inputs, no analytics requests leave the page.
Frequently asked questions
How does the CCTV NVR storage planner calculate total storage?
Total storage (TB) = cameras x bitrate per camera (Mbps) x 3600 seconds x hours per day x retention days x motion factor x safety buffer, divided by 8 (bits to bytes) and by 1e12 (bytes to TB). For example, 8 cameras at 4 Mbps, 24 h/day, 30 days = 8 x 4 x 3600 x 24 x 30 / 8 / 1e12 = 10.37 TB. The planner tab does exactly this math live, including motion-detection savings and a 10-20% safety buffer.
How much storage do I need for 4 cameras recording 30 days?
It depends on bitrate. At 2 Mbps per camera (typical 1080p H.265): 4 x 2 x 3600 x 24 x 30 / 8 / 1e12 = 2.59 TB. At 4 Mbps per camera (typical 4MP H.265): 5.18 TB. Use the NVR planner tab with your resolution, fps and codec to get your exact number, then pick a drive size from the drive-recommendation table (e.g. 1x 8 TB drive covers the 2.59 TB case with room to spare).
How many days will 1 TB record 4 cameras?
With 4 cameras at 2 Mbps each (8 Mbps total): 1e12 x 8 bits / (8e6 bits/s) / 3600 = 277.8 hours, which is 11.6 days of 24-hour recording. Halve the bitrate or record 12 hours/day and it doubles. The recording-time tab inverts any capacity: enter TB and total bitrate to get hours and days.
How much video can 1 TB store from one camera?
At 2 Mbps (typical 1080p H.265 stream): 1e12 x 8 / (2e6 x 3600) = 1,111 hours (46.3 days continuous). At 4 Mbps: 555.6 hours (23.1 days). At 8 Mbps (4K): 277.8 hours (11.6 days). These are continuous-recording figures; motion-triggered recording stretches them further.
How much storage does H.265 save compared to H.264?
For the same quality, H.265 (HEVC) typically needs about half the bitrate of H.264 - roughly a 2:1 storage ratio. Example: 8 cameras x 1080p x 25 fps x 30 days at ~4 Mbps H.264 = 10.37 TB; the same at ~2 Mbps H.265 = 5.18 TB. H.265+ / Smart H.265 typically saves another 20-30% on top. Note these are typical values; real savings depend on scene complexity.
Are H.265+ / Smart H.265 70% savings claims real?
Treat vendor "up to 70%" claims as best-case marketing: they are measured on static, low-noise scenes where the smart codec can aggressively compress the background. On busy scenes the saving is much smaller. This tool uses a conservative typical H.265+ model (~3:1 vs H.264 baseline bit-per-pixel, i.e. about 1.5x better than plain H.265) and labels every vendor preset as typical. Plan with a safety buffer rather than a best-case claim.
How much storage does motion detection recording save?
Motion-triggered recording saves storage in proportion to how quiet the scene is: a busy entrance (80% motion) might save only 10-20%, while a storage room (5% motion) can save 70-90%. The planner lets you set motion savings from 0 to 90%; typical installers plan for 40-60% savings on general-purpose cameras. Smart motion (human/vehicle detection, e.g. Hikvision Motion Detection 2.0) cuts false alarms but does not change the bitrate math.
What are typical bitrates for Dahua cameras?
Dahua publishes reference bitrates in its DSS decode-performance documents (main stream, 30 fps): 720p H.264 ~2 Mbps / H.265 ~1 Mbps; 1080p H.264 ~4 Mbps / H.265 ~2 Mbps; 4MP (2688x1520) H.264 ~8 Mbps / H.265 ~2 Mbps; 8MP (4K) H.264 ~8 Mbps / H.265 ~4 Mbps. The vendor-presets tab applies these and equivalents for Hikvision, Axis, Bosch, Hanwha, UniFi and Reolink - all labeled typical, since VBR and scene complexity make real rates vary.
What are typical bitrates for Hikvision cameras?
Hikvision specs give wide ranges (e.g. 32 Kbps to 8 Mbps), so planners use mid-typical values: 1080p ~4 Mbps H.264 / ~2 Mbps H.265, 4MP ~6 Mbps H.264 / ~3 Mbps H.265, 4K ~10 Mbps H.264 / ~5 Mbps H.265 at 25 fps. With H.265+ enabled these drop roughly 30%. The vendor tab has one-click presets for Hikvision and six other brands.
How long can a GoPro record 4K on a 128 GB card?
Recording time = card size x 8 / bitrate / 3600. At a typical 45 Mbps for 4K30 (H.265): 128e9 x 8 / (45e6 x 3600) = 6.32 hours. At 60 Mbps for 4K60: 4.74 hours. At 100 Mbps for 5.3K60: 2.84 hours. The SD-card tab computes this for 32-1024 GB cards across GoPro, DJI and dashcam presets - note battery life usually runs out long before the card does.
How much can a dashcam record on a 256 GB card?
Dashcams typically record 1080p at 6-12 Mbps (8 Mbps is a common setting), 1440p at 12-20 Mbps, and 4K at 25-40 Mbps. At 8 Mbps: 256e9 x 8 / (8e6 x 3600) = 71.1 hours. At 30 Mbps 4K: 18.9 hours. A dual-channel 1080p+1080p dashcam (~16 Mbps total) gets about 35.6 hours on 256 GB. Use high-endurance microSD cards for continuous loop recording.
What does 30-day video retention mean for CCTV?
Video retention is how many days of footage your system keeps before overwriting the oldest video - many businesses require 14 to 30 days for insurance or compliance. The planner computes retention directly: enter your camera count, bitrate, hours/day and target days, and it tells you the TB needed. Conversely, the recording-time tab answers "my NVR has 6 TB - how many days do my 8 cameras cover?"
Does lowering frame rate from 30 to 15 fps halve storage?
Almost exactly. Bitrate scales linearly with frame rate (bitrate = pixels x fps x bits-per-pixel), so 15 fps needs half the bitrate of 30 fps at the same resolution and codec. Many installers run 12-15 fps for general surveillance - enough to identify people, half the storage of 30 fps. The planner lets you set any fps from 1 to 60 and shows the effect instantly.
What hard drive size do I need for an NVR?
Compute your total TB, then round up to standard surveillance drive sizes: 4, 8, 10, 12, 16, 18 or 20 TB. The planner's drive table shows how many drives of each size you need (e.g. 10.37 TB needs 2x 8 TB or 1x 12 TB) and adds a 10-20% safety buffer because VBR recording and scene changes make real usage vary. Use surveillance-rated drives (e.g. WD Purple, Seagate SkyHawk) designed for 24/7 writing.
Why do different CCTV storage calculators give different answers?
Because bitrate is not a fixed property - VBR encoders vary it with scene motion, lighting and noise, and "typical" presets differ between tools. Honest calculators (like this one) show the formula, label presets as typical, and add a 10-20% safety buffer. Any calculator that gives a single exact number without showing its bitrate assumption is hiding its guess.
How can I reduce my CCTV storage requirements?
Six levers, biggest first: (1) switch H.264 to H.265 (~50% saving), (2) enable motion-triggered recording (up to 90% in quiet scenes), (3) drop 30 fps to 15 fps (~50%), (4) use smart codecs (H.265+/Zipstream/WiseStream, ~20-30% on top), (5) record on a schedule instead of 24/7, (6) lower resolution on low-priority cameras. The codec-and-motion explainer tab compares H.264 vs H.265 vs H.265+ side by side for your exact camera count.