Bitrate calculation for 4K cameras is where retail projects fail the most: nobody sizes with real codec, everyone assumes H.264 and ends up with disks at 80% in 2 weeks. This is the correct formula, the real codecs, and the numbers that apply to your store.
( spoiler: a 4K@30fps camera in real H.265 does not generate 6 Mbps sustained — it generates between 1.5 and 4 Mbps depending on scene and vendor codec )
The exact formula
Bitrate per camera (Mbps) = resolution × fps × compression factor × scene factor
Where:
- resolution: in total pixels (3840×2160 = 8,294,400 for 4K)
- fps: frames per second (10, 15, 25, 30)
- compression factor: depends on codec (H.264=1.0, H.265=0.5, Smart H.265+=0.35, WiseStream II=0.30, Zipstream=0.30)
- scene factor: depends on motion (static=0.5, normal=1.0, high=1.5)
Storage per camera (TB/day) = (bitrate × 3600 × 24) / 8 / 1024 / 1024 / 1024
Multiply by number of cameras × retention days = total storage.
Concrete numbers for 4K@30fps
Assuming scene factor = 1.0 (typical retail operation, 60% static time + 40% traffic time):
| Codec | Sustained bitrate | Storage 24h | Storage 30 days | Storage 60 days |
|---|---|---|---|---|
| H.264 | 12 Mbps | 129 GB | 3.87 TB | 7.74 TB |
| H.265 (HEVC) | 6 Mbps | 65 GB | 1.94 TB | 3.87 TB |
| Smart H.265+ (Dahua) | 4 Mbps | 43 GB | 1.29 TB | 2.58 TB |
| WiseStream II (Hanwha) | 3.5 Mbps | 38 GB | 1.13 TB | 2.27 TB |
| Zipstream (Axis) | 3 Mbps | 32 GB | 0.97 TB | 1.94 TB |
Real scene factor in 24/7 retail store:
- Parking lot at night: factor 0.3 (almost nothing moves)
- Store aisle at night: factor 0.4
- Store entrance day: factor 1.5 (heavy traffic)
- Point of sale day: factor 1.3
- Warehouse day: factor 0.7
If you weight 60% of the day as “static” and 40% as “high activity”, the weighted average factor is ~0.85, not 1.0. That reduces the real storage vs the table above by ~15%.
Practical example: retail store with 16 4K cameras
Assume 50% active 4K cameras + 50% support 2MP cameras, all in H.265 with Dahua Smart H.265+:
| Camera | Count | Bitrate | Storage/day | Storage/30d |
|---|---|---|---|---|
| 4K@30fps Smart H.265+ | 8 | 4 Mbps | 43 GB | 1.29 TB |
| 2MP@15fps H.265 | 8 | 1 Mbps | 11 GB | 0.32 TB |
| TOTAL | 16 | — | 432 GB/day | 12.96 TB |
For 60-day retention (high-shrinkage retail category): ~26 TB. For 90-day retention (electronics, cosmetics category): ~39 TB.
Example: retail store with 32 4K cameras (CEDIS or anchor store case)
| Camera | Count | Bitrate | Storage/day | Storage/30d |
|---|---|---|---|---|
| 4K@30fps WiseStream II Hanwha | 32 | 3.5 Mbps | 38 GB | 1.13 TB |
| TOTAL | 32 | — | 1216 GB/day | 36.5 TB |
With RAID 5 (1 parity disk per 4 data disks), you need 5 disks of 10 TB = 50 TB raw → 40 TB usable. Approximate cost: $1,500 USD per 10 TB surveillance-grade disk (Seagate Skyhawk or WD Purple). Total: $7,500 USD on storage alone.
Common sizing errors
Error 1: Assume H.264 when cameras are already H.265 If your RFQ says “32 4K cameras @ 30fps” without codec specified, many integrators assume H.264 = 12 Mbps. The reality with H.265 + vendor codec is 3.5-4 Mbps. You over-size by 3-4× the storage. Wasted cost: $5,000-10,000 USD per project.
Error 2: Not considering real scene factor Assuming factor 1.0 (always max activity) over-sizes ~15-20%. Assuming factor 0.3 (almost always static) under-sizes and the disk fills before 30 days.
Error 3: Forgetting metadata and event overhead VMS, motion events, analytics metadata add ~5-10% overhead to the video bitrate. If you do not consider it, you fall short.
Error 4: RAID poorly sized RAID 5 with 4 disks of 10 TB = 30 TB usable (1 parity disk). RAID 6 with 6 disks = 40 TB usable (2 parity disks). The difference is 33% more useful capacity for the same disk count in RAID 6 with larger disks. For CCTV, RAID 6 is the modern standard because it tolerates 2 simultaneous disk failures.
Error 5: Confusing decimal TB with binary TB A “10 TB” disk shows up as ~9.09 TiB (tebibytes, factor 1024) in the operating system. Your VMS reports bytes consumed in TiB. The gap is 10%. If you size to the exact TB without padding, you fall short.
Vendor calculation tools
The three tools I use in projects:
- Axis Zipstream calculator: https://www.axis.com/tools/zipstream-calculator (reference for Axis lines, also serves as a benchmark for any H.265 camera)
- Hanwha Storage calculator: https://www.hanwhavision.com/en/tools/storage-calculator/
- Seagate Surveillance calculator: https://www.seagate.com/internal-hard-drives/surveillance-hdd/
The three calculators start from different assumptions (Axis assumes Zipstream, Hanwha assumes WiseStream II, Seagate assumes pure H.264). For a real RFQ, run all three with your codec and scene, average, and add 15% padding.
Executive summary
For a retail store with 16 4K cameras and 30-day retention: ~13 TB usable. You need 2 disks of 10 TB in RAID 1, or 4 disks of 5 TB in RAID 5. For 32 4K cameras and 30 days: ~36 TB usable. 5 disks of 10 TB in RAID 5, or 4 disks of 14 TB in RAID 6. For 64 4K cameras and 90 days (electronics vertical): ~155 TB. Enterprise solution: NAS with 8+ disks in RAID 6 + cold storage archive tier after 30 days.
P.D. Does your current RFQ include codec and real scene factor? If not, you over-size or under-size by 2-3×. The difference between quoting well and wrong is easily $5,000 USD per store.
Frequently asked questions
How much storage does a 4K camera need in 24/7 operation? With H.265 standard and typical 6 Mbps bitrate: ~64 GB/day. With Zipstream (Axis) or H.265+ (Hikvision) in static scene: ~30 GB/day. Realistic 24/7 average with 50% static scene: 45-50 GB/day. For 30 days retention: 1.4-1.5 TB per camera. Multiply by number of cameras: 50 cameras = 70-75 TB total. RAID overhead 25-30% extra, plus 20% for hot spare. Total: ~110 TB for 50 cameras / 30 days.
Does H.265 reduce storage vs H.264? Yes, 40-50% in typical conditions. H.264 at 4K@20fps: 10-12 Mbps. H.265 at 4K@20fps: 5-7 Mbps. The difference is larger in static scene (50-60% less) and smaller in high-motion scene (20-30% less). For a deployment with 50% static and 50% motion, H.265 gives you 40% average savings. It’s the best ROI storage upgrade in CCTV.
Is H.265+ or Zipstream worth it? Yes, marginally. Hikvision’s H.265+ reduces 20-30% additional over H.265 standard. Axis’s Zipstream reduces 30-50% additional. On a 50-camera deployment, Zipstream saves you 20-30 TB of storage at 30 days — that’s $2K-3K USD in disks + rack space saved. The question is whether your vendor offers it free (Axis includes Zipstream in firmware) or charges extra (Hikvision H.265+ comes free but requires their proprietary NVR for max compression).
How much does total storage cost? For 50 4K cameras at 30 days: $4K-7K USD in disks (8-10 disks of 12-16 TB). Plus $1K-2K USD in enclosure/NAS. Total: $5K-9K USD. That storage must have (1) RAID-6 or RAID-60 for fault tolerance, (2) UPS for voltage spikes, (3) backup to object storage (AWS S3, Wasabi) if you have SLA >30 days. For 60 days: double the cost. For 90 days: triple.
What about NVRs or VMS? For 50 4K cameras you need a VMS with 4-8 GB RAM per stream (decoding) + 200-300 Mbps throughput. Typical VMS: Milestone (free up to 8 cameras, then per-camera license), Genetec Security Center ($200-500/camera license + server), Avigilon ($300-600/camera), open-source Shinobi/Zoneminder ($0 software + server cost). Server hardware: $3K-6K USD for one that handles 50 4K streams. Total VMS+server: $8K-25K USD depending on vendor.
What if I already have 1080p cameras and want to migrate to 4K? Don’t migrate everything to 4K. 4K costs 3-4× more in storage and 2-3× more in bandwidth per camera. The rule: 4K in zones where you need fine detail (facial identification at >5m, car plates, cash registers), 1080p in general coverage zones. In a typical deployment: 30-40% 4K cameras + 60-70% 1080p. Your total storage is 50-60% of the all-4K equivalent, with the same level of detail in critical zones.
Sources
[1] Axis Communications — Zipstream bandwidth calculator — https://www.axis.com/tools/zipstream-calculator [2] Hanwha Vision — WiseStream II whitepaper — https://www.hanwhavision.com/en/learning-center/white-papers/ [3] Seagate — Surveillance HDD calculator — https://www.seagate.com/internal-hard-drives/surveillance-hdd/ [4] CCTVInfo — H.264 vs H.265 vs H.265+ for CCTV (2026) — https://cctvinfo.com/guides/h264-vs-h265 [5] Western Digital — Purple Drive surveillance storage calculator — https://www.westerndigital.com/products/internal-drives/wd-purple-hdd [6] IPVM — Storage calculation methodology and error analysis — https://ipvm.com/reports/storage-calculation [7] Hanwha Vision — Storage calculator tool — https://www.hanwhavision.com/en/tools/storage-calculator/