How to Use This CCTV HDD Calculator
Plan the right hard disk for your DVR or NVR before you buy. Enter camera count, resolution, FPS, codec, and how long you need footage retained. The tool estimates total storage and suggests the next standard HDD size with spare capacity.
- Enter the number of cameras and choose resolution (or a custom bitrate).
- Set FPS and pick H.264 or H.265.
- Choose continuous or motion recording, hours per day, and retention days.
- Read the recommended HDD size and per-day / per-camera breakdown.
CCTV Storage Formula
Storage Required
GB = Bitrate (Mbps) × Cameras × Hours × Days × 3600 ÷ (8 × 1000)
Example: 2 Mbps × 4 cams × 24 hrs × 7 days = 604.8 GB
Recommended Drive
Add ~12% overhead, then round up to the next common HDD size (1, 2, 4, 6, 8, 10, 12, 16, 18, 20 TB).
Example: 604.8 GB + overhead → recommend 1 TB
Hikvision Recommended Bitrate @ 25 FPS
| Resolution | H.264 | H.265 |
|---|---|---|
| 720p (1 MP) | 2 Mbps | 1 Mbps |
| 1080p (2 MP) | 4 Mbps | 2 Mbps |
| 3 MP | 6 Mbps | 3 Mbps |
| 4 MP | 8 Mbps | 4 Mbps |
| 5 MP | 10 Mbps | 5 Mbps |
| 4K / 8 MP | 16 Mbps | 8 Mbps |
Bitrates follow Hikvision’s recommended bit-rate table and scale with FPS. Actual usage varies by scene complexity and camera settings.
CCTV HDD Calculator — Frequently Asked Questions
How is CCTV hard disk storage calculated?
Storage is estimated from bitrate × cameras × recording hours × retention days, converted from megabits per second into gigabytes over the full retention window.
Does H.265 save more storage than H.264?
Yes. H.265 (HEVC) typically uses about 40–50% less bitrate than H.264 at similar visual quality, which reduces the hard disk size needed.
How much HDD do I need for 8 cameras for 30 days?
It depends on resolution, FPS, and codec. As a rough guide, four 1080p cameras on H.265 at 25 FPS recording 24 hours for 7 days need about 605 GB (recommend 1 TB). Eight 1080p H.264 cameras for 30 days often need around 10–12 TB. Use this calculator for an exact estimate.
Should I buy a larger HDD than the calculated size?
Yes. Leave 10–15% free space for the NVR/DVR filesystem, indexing, and bitrate spikes. This calculator already recommends the next standard drive size with overhead.
Is this CCTV HDD calculator free?
Yes. The TRULINK CCTV HDD calculator is free, works in your browser, and requires no registration.
Need CCTV Installation or Storage Planning?
TRULINK designs and installs CCTV, NVR, and enterprise networking solutions across Gurgaon and Delhi NCR.