How CCTV Network Bandwidth Is Calculated
Every IP camera pushes a continuous video stream onto the network. Its bitrate depends on four things: resolution, frame rate, compression codec and encoding quality. Network bandwidth determines the switch uplinks and NVR spec, while the same bitrates over time determine hard-disk size — that half of the design lives in our CCTV Storage Calculator.
Per-camera Mbps = Base Bitrate × (FPS ÷ 25) × Codec Factor × Quality Factor
Total Bandwidth = Σ (Per-camera Mbps × Quantity)
Design Bandwidth = Total × (1 + Headroom %)
Base bitrates are H.264 medium-quality figures at 25 fps. The codec factor is 1.00 for H.264 and 0.55 for H.265 (HEVC) — the same ~45% saving used in the storage calculator. The quality factor is 0.75 (low), 1.00 (medium) or 1.30 (high).
Worked Example: 20-Camera Office Building
16 × 2 MP dome cameras and 4 × 4 MP entrance cameras, all at 25 fps, H.265, medium quality, 30% headroom, 2 remote viewers on D1 sub-streams:
- 2 MP per camera: 4.0 × (25÷25) × 0.55 × 1.00 = 2.20 Mbps → 16 cams = 35.2 Mbps
- 4 MP per camera: 8.0 × 0.55 = 4.40 Mbps → 4 cams = 17.6 Mbps
- Total camera bandwidth = 35.2 + 17.6 = 52.8 Mbps (also the NVR incoming load)
- Design bandwidth = 52.8 × 1.30 = 68.6 Mbps
- Remote viewing WAN upload = 2 × 1.0 = 2.0 Mbps
68.6 Mbps fits under the ~80 Mbps practical limit of a 100 Mbps link — workable, but a Gigabit uplink is the sensible choice so the network never becomes the bottleneck as cameras are added.
Camera Bitrate Quick Reference (25 fps, Medium Quality)
| Resolution | H.264 Bitrate | H.265 Bitrate | Cameras per Gigabit uplink* |
|---|
| 1 MP (720p) | 2.0 Mbps | 1.1 Mbps | ≈ 550 |
| 2 MP (1080p) | 4.0 Mbps | 2.2 Mbps | ≈ 280 |
| 3 MP | 6.0 Mbps | 3.3 Mbps | ≈ 185 |
| 4 MP | 8.0 Mbps | 4.4 Mbps | ≈ 140 |
| 5 MP | 10.0 Mbps | 5.5 Mbps | ≈ 110 |
| 6 MP | 12.0 Mbps | 6.6 Mbps | ≈ 95 |
| 8 MP / 4K | 16.0 Mbps | 8.8 Mbps | ≈ 70 |
| 12 MP | 24.0 Mbps | 13.2 Mbps | ≈ 47 |
*H.265, at 80% link utilisation with 30% design headroom applied. Actual capacity depends on switch backplane and network design.
CCTV Network Design Tips
- Keep sustained utilisation below 80% of any link — VBR encoding produces I-frame bursts well above average bitrate.
- Segment CCTV on its own VLAN (or physically separate switches) so surveillance traffic never competes with corporate data.
- Check the NVR's incoming-bandwidth spec, not just channel count. A "32-channel" NVR rated 160 Mbps incoming cannot record 32 × 4K cameras at full bitrate.
- Check the PoE budget separately — a 24-port PoE switch with a 190 W budget cannot power 24 IR bullet cameras drawing 12–15 W each (IEEE 802.3af/at/bt classes matter).
- Uplinks aggregate; access ports don't. Each camera on its own 100 Mbps access port is fine — the uplink from switch to NVR/core carries the sum, and that's what this calculator sizes.
- Use sub-streams for live video walls — a 16-camera wall pulling main streams can double network load unnecessarily.
- Back up the head-end: NVR, core switch and monitors need UPS autonomy — size it with our UPS Sizing Calculator. Recording capacity in days lives in the CCTV Storage Calculator.
Frequently Asked Questions
How much bandwidth does one IP CCTV camera use?
A typical 2 MP (1080p) camera uses about 4 Mbps with H.264 at 25 fps and medium quality, or roughly 2.2 Mbps with H.265. A 4 MP camera needs about 8 Mbps (H.264) and an 8 MP / 4K camera about 16 Mbps (H.264). Actual bitrate also depends on scene motion and encoder settings.
How much bandwidth does H.265 save vs H.264?
Typically 40–50% at the same visual quality. This calculator uses a 0.55 factor — H.265 needs about 55% of H.264 bandwidth. "Smart" codecs (H.265+/H.264+) can save even more on static scenes.
What is network headroom and why 30%?
Camera bitrates are averages — motion, night-time noise and I-frame bursts push instantaneous bitrate well above them. A 25–30% margin keeps links below sustained saturation and leaves room for viewing streams and future cameras.
Do I need a Gigabit switch for CCTV?
Keep sustained traffic below ~80% of link capacity. A 100 Mbps uplink supports roughly 80 Mbps of design bandwidth — around 35 × 2 MP H.265 cameras. Beyond that, or with any 4K cameras, use Gigabit access switches with Gigabit or 10G uplinks.
How much internet speed for remote viewing?
Remote apps pull the sub-stream, not the main stream. Budget ~1 Mbps of upload per concurrent D1/540p stream (2 Mbps for 720p). Four simultaneous viewers on D1 need about 4 Mbps site upload speed.
Disclaimer: Preliminary estimates based on typical camera bitrates. Actual bitrates vary with scene complexity, motion, lighting, encoder implementation and smart-codec features. Verify against manufacturer bitrate tables and NVR/switch specifications before final network design.