Free tool · DVR & NVR
CCTV storage calculator: how big a hard disk you need
Enter your cameras, their resolution and how many days of footage you want to keep. The calculator tells you the hard disk size for your DVR or NVR — and how long a 1TB, 2TB or 4TB drive will actually last.
- H.264, H.265 & H.265+
- 2MP to 8MP (4K)
- No sign-up
Calculate your CCTV hard disk size
Recommended hard disk
4 TB
30 days of recording from 4 cameras needs about 2.8 TB of drive capacity.
- Per day
- 86 GB
- Per camera
- 2.0 Mbps
- All cameras
- 8.0 Mbps
How long each drive lasts
- 1 TB10 days
- 2 TB21 days
- 4 TB43 days
- 6 TB64 days
- 8 TB86 days
- 10 TB107 days
An estimate from typical camera bitrates. Busy scenes, night noise and rain push real usage up, so we size drives with headroom on every survey.
Get it sized on a free surveyQuick reference
How many days of recording does 1TB, 2TB or 4TB hold?
Continuous recording, 25 fps, H.265 — the most common setup we find in Chennai homes, shops and apartment blocks. Use the calculator above for anything else.
| Cameras | 1 TB | 2 TB | 4 TB | 8 TB |
|---|---|---|---|---|
| 4 × 2MP | 10 days | 21 days | 43 days | 86 days |
| 4 × 4MP | 7 days | 14 days | 28 days | 57 days |
| 8 × 2MP | 5 days | 10 days | 21 days | 43 days |
| 8 × 4MP | 3 days | 7 days | 14 days | 28 days |
| 16 × 2MP | 2 days | 5 days | 10 days | 21 days |
| 16 × 4MP | 1 day | 3 days | 7 days | 14 days |
Per camera
Storage one CCTV camera uses in a day
Continuous recording at 25 fps. Multiply by your camera count, then by the days you want to keep.
| Resolution | H.264 | H.265 | H.265+ (smart) |
|---|---|---|---|
| 2MP | 43 GB | 22 GB | 11 GB |
| 3MP | 54 GB | 27 GB | 14 GB |
| 4MP | 65 GB | 32 GB | 16 GB |
| 5MP | 86 GB | 43 GB | 22 GB |
| 8MP | 173 GB | 86 GB | 43 GB |
Working it out by hand
The CCTV storage formula
Every storage calculator, including this one, runs the same arithmetic. Here it is, so you can check a quote yourself.
GB per day = bitrate (Mbps) × cameras × hours × 0.45
Drive size (TB) = GB per day × days ÷ 1,000 ÷ 0.93
0.45 turns one Mbps for one hour into gigabytes (3,600 seconds ÷ 8 bits ÷ 1,000). 0.93 allows for the space a drive loses to formatting — a “1 TB” disk shows about 930 GB in a recorder.
Worked example: four 2MP cameras, 30 days
- 01A 2MP camera on H.265 records at about 2 Mbps.
- 022 × 4 cameras × 24 hours × 0.45 = 86 GB a day.
- 0386 GB × 30 days ÷ 1,000 ÷ 0.93 = 2.8 TB.
- 04The next standard size up is a 4TB surveillance drive.
Before you buy a bigger drive
Four ways to keep more days without losing evidence
- 01
Switch the cameras to H.265 or H.265+
Often a setting, not a purchase. It halves storage against H.264 with no visible loss.
- 02
Record quiet areas on motion
Keep gates, doors and cash counters continuous. Terraces, stores and back corridors rarely need to be.
- 03
Drop to 15 fps where nothing moves fast
Corridors and parking still look smooth at 15 fps and use about 40% less than at 25.
- 04
Match resolution to the job
An 8MP camera over an empty terrace fills a drive four times faster than a 2MP one and tells you nothing more.
Questions
CCTV storage, asked and answered
Rather have it sized for you? The survey is free.
An engineer checks every camera position, the recorder and the drive, and sets retention to the number of days you actually need — anywhere in Chennai.