CCTV DVR Storage Calculator: How Big a Drive Does Your Shop Need?
Quick answer: for a typical small shop running six cameras at 1080p with H.265+, a 4 TB surveillance drive holds roughly 24 days of continuous footage — enough to cover a dispute you only hear about a fortnight later. The maths for your exact CCTV DVR storage calculator numbers is below.
If you run a shop, storage is not an abstract spec — it decides whether the footage still exists when you need it. A till discrepancy usually surfaces at the weekly cash-up; a stockroom loss might only show at a monthly count. If your drive overwrites after six days, the evidence is gone before the question is even asked. The answer depends on four variables: camera count, resolution, frame rate and compression codec.
Community posts on r/cctv reveal the same pattern: owners install eight cameras over the till, stockroom and shopfront, pick a drive that worked for a desktop PC, then discover playback stutters or retention lasts only a few days. Others report live view works but archived footage will not load — often a failing surveillance drive pushed beyond its write endurance. Getting storage right at purchase means the recording is there when the awkward conversation happens.
The Storage Formula (Simplified)
Daily storage (GB) ≈ (cameras × bitrate in Mbps × 86400 seconds) ÷ (8 × 1024). In practice, use these rule-of-thumb bitrates for H.265+ at 1080p:
- Low traffic (10 fps): ~1.5 Mbps per camera
- Standard (15 fps): ~2.5 Mbps per camera
- High detail (20 fps): ~4 Mbps per camera
Example: a small shop with four 1080p cameras at 15 fps ≈ 10 Mbps combined ≈ 108 GB per day. A 2 TB drive yields roughly 18 days before overwrite — matching the guidance on our 8-Channel HD CCTV DVR Recorder product page (2 TB + 4 cameras at 1080p ≈ 14–21 days with H.265+). Footage stays on your own drive in the back office — no cloud plan, no monthly fee, nothing held by a third party.
Quick Reference Table (H.265+, 1080p, 15 fps)
| Cameras | 2 TB drive | 4 TB drive | 6 TB drive |
|---|---|---|---|
| 4 cameras | ~18 days | ~36 days | ~54 days |
| 6 cameras | ~12 days | ~24 days | ~36 days |
| 8 cameras | ~9 days | ~18 days | ~27 days |
Figures assume continuous recording. Motion-only schedules can double effective retention on low-activity sites.
Why Surveillance Drives Matter
Desktop HDDs are optimised for occasional reads and writes. A CCTV DVR writes continuously, 24 hours a day, seven days a week. Surveillance-rated drives (Seagate SkyHawk, WD Purple, Toshiba S300) tolerate higher write workloads and reduce the risk of premature failure that forum users describe when playback suddenly stops but live view still works.
Our 8-channel DVR accepts a user-installed surveillance drive in its internal bay. Choose capacity based on the table above, then format through the recorder menu — never assume a PC-formatted drive is ready for CCTV duty.
Frame Rate vs Retention: What UK Buyers Actually Need
15 fps is sufficient for the shop door, aisle overviews and the street frontage. Drop to 10 fps on the stockroom or rear yard where footfall is low. Reserve 20 fps for the till and cash-handling zones — when a refund dispute or a suspected sweethearting incident comes down to what a hand actually did, frame-by-frame clarity is the difference between an answer and a shrug.
One r/cctv poster with thirteen 8 MP cameras asked whether frame rate or drive size mattered more — the honest answer is both, but reducing fps on non-critical channels often frees enough space to avoid buying a second drive immediately.
Compression: H.264 vs H.265+
H.265+ (High Efficiency Video Coding) cuts bitrate roughly in half compared with H.264 at the same visible quality. Our recorder supports H.265+ compression, which is why a 2 TB drive stretches further than older DVRs using H.264 only. If you migrate footage from a legacy unit, expect storage needs to jump until you enable H.265+ on the new box.
How Long Should a Shop Keep Footage?
- Card disputes and chargebacks: customers have weeks to raise them — 30+ days of retention means you can still pull the transaction from the till camera.
- Stock loss: if you only count monthly, a 2 TB drive on eight cameras (~9 days) is useless for tracing when items walked. Size for your counting cycle, not the default.
- Insurance and police follow-up: a break-in report rarely completes in a week. Officers asking for footage a fortnight later is normal; plan retention so you are not apologising.
One legal note: under UK GDPR, ICO guidance says business CCTV footage should be kept no longer than necessary for its purpose — there is no fixed statutory period, and around 30 days is a common working practice in retail. Whatever period you choose, your drive has to be big enough to actually deliver it.
Build your system: Start with the 8-Channel HD CCTV DVR Recorder (8 BNC inputs, H.265+, £342.50, 12-month UK warranty). Pair it with a 4 TB surveillance HDD for 30-day retention on a six-camera shop, or 2 TB if you are starting with four cameras. Fitting it is a DIY job — see the 8 channel DVR setup guide.
Frequently Asked Questions
Can I use an SSD instead of an HDD in my DVR?
Most standalone DVRs expect 3.5-inch surveillance HDDs. SSDs are uncommon in eight-channel units and offer no practical benefit for sequential video writes — capacity per pound favours HDDs.
What happens when the drive is full?
The DVR overwrites the oldest footage automatically (rolling recording). Increase drive size or reduce fps/bitrate if you need longer retention before overwrite.
Can I view footage if I remove the drive and plug it into my PC?
No. CCTV drives use proprietary file systems. Playback requires the original DVR or manufacturer export tools — another reason to keep the recorder online and backed up via export for critical incidents.