HDD Size Calculator
Enter the number of cameras, their resolution and codec, the frame rate, how many hours a day they record, how many days to keep and how much of the time they actually record. The calculator gives the storage needed and the drive to buy.
- CCTV storage
- H.264 or H.265
- Days of recording
Set recording share below 100% if cameras only record on motion. 30% to 50% is typical for a quiet home.
CCTV storage depends on bitrate, cameras and days. A 1080p camera using H.265 at 25 frames a second records about 2.2 Mbps, roughly 24 GB a day. Four cameras kept for 30 days need nearly 3 TB.
CCTV storage chart
4 cameras, 24 hours, 30 days, H.265. Search for a resolution.
| Resolution | Per camera (Mbps) | Per day (GB) | 30 days (TB) |
|---|---|---|---|
| 720p | 1.1 | 48 | 1.43 |
| 1080p | 2.2 | 95 | 2.85 |
| 4 MP | 3.3 | 143 | 4.28 |
| 5 MP | 4.4 | 190 | 5.7 |
| 4K | 6.6 | 285 | 8.55 |
Bitrates vary with the scene. These are typical figures.
Days and storage
4 cameras, 1080p, H.265. Slide the days to keep.
The recorder shows how many drives the storage needs.
How to size CCTV storage
Bitrate to terabytes. Step through it.
Bitrate
By resolution and codec.
Many recorders overwrite the oldest footage when full, so the drive size sets how far back you can look.
Continuous, motion or scheduled
Recording modes. Compare them.
Records all the time.
Records on movement.
Set hours only.
Motion recording saves space, but set it carefully so it does not miss the start of an event.
Before buying
Storage checks. Tick each item.
Tick each item as you go.
Surveillance drives such as WD Purple or Seagate SkyHawk are built to write all day, unlike desktop drives.
What you get
CCTV storage. Each tile explains one result.
TB.
To buy.
Mbps and GB a day.
GB a day.
Days.
H.265 roughly halves storage compared with H.264 for the same picture quality.
Frequently Asked Questions
No question matches that search.
How much storage do I need for CCTV?
Cameras × bitrate × seconds recorded × days, divided by 8. Four 1080p H.265 cameras need about 3 TB for 30 days.
How many days will a small drive record?
A 1 TB drive holds about 10 days from four 1080p H.265 cameras recording all day.
Does the newer codec save storage?
Yes. H.265 uses about 40% to 50% less than H.264.
How much storage does an ultra HD camera use?
A 4K camera uses about 6.6 Mbps with H.265, around 70 GB a day.
Does motion recording save space?
Yes, often half or more, depending on how busy the scene is.
What hard drive is best for CCTV?
A surveillance-rated drive built for constant writing.
How long should I keep CCTV footage?
Often 30 days, but check local rules on keeping recordings.
Footage when you need it
Work out storage from your cameras and how long you keep footage, then fit surveillance drives with room to spare. The recorder will hold the days you need.
More size calculators
Each one has its own calculator, worked examples and answers to common questions.