Security camera storage calculator
Enter your cameras in groups and your recorder's drives: this CCTV storage calculator gives the days of video the drives keep, the storage written each day and the drive layouts that reach your retention goal.
Examples, not measurements. Pick the closest, then change anything.
Each drive adds its full size. One failed drive loses its share of the video. Ask which layout your recorder uses.
Advanced assumptions
Typical: 0 to 40. Default 0, as in the guide. Bitrate rises with motion, rain and night grain; in the guide's example a rainy day wrote 37 percent more on a street camera. Adds to every group.
Typical: 0 to 5. Default 0: the guide uses the full drive. Formatting and any space a recorder keeps for itself trim a little; check the free space your recorder reports.
37.0days of video on these drives
About 5 weeks. Oldest video on the drives today: Oct 3, 2026.
Meets the 30 day goal
- Written a day, all 8 cameras
- 216.0 GBabout 6.48 TB a month
- Usable storage for 30 days
- 6.48 TB
- Usable on 1 × 8 TB, single drives
- 8.00 TBShows as about 7.28 TB in a menu that counts in binary units
- Recording bandwidth
- 20 Mbpsinto the recorder, all day
- Your single drive1 × 8 TB8.00 TB, 37.0 days
- 2 drives, mirrored2 × 8 TB8.00 TB, 37.0 days
- 4 drives, RAID 54 × 3 TB9.00 TB, 41.7 days
- 8 drives, RAID 68 × 2 TB12.00 TB, 55.6 days
Smallest common drive size for each layout. Check the largest drive your recorder accepts.
- All cameras8 × 2.5 Mbps216.0 GB100%
An estimate from the inputs above; a site survey sets the real numbers.
- All cameras: 2.5 Mbps (4MP, H.265 at 15 fps)
- 2.5 Mbps × 86,400 s ÷ 8 ÷ 1,000 = 27.0 GB a camera; × 8 = 216.0 GB a day
- Usable: 1 drive × 8,000 GB = 8,000 GB
- Days = 8,000 GB × 1,000 × 8 ÷ ((2.5 × 8) Mbps × 86,400 s) = 64,000,000 ÷ 1,728,000 = 37.0 days
- Goal: 216.0 GB × 30 days = 6,480 GB, 6.48 TB usable
How to use the security camera storage calculator
- Pick the example building closest to yours, or keep the small building.
- Make one group for each kind of camera: the same resolution, codec, frame rate and recording mode. Set how many cameras are in each group.
- If your recorder shows a camera's bitrate, choose "Own bitrate" and enter it.
- Enter the drives: how many, what size, and the layout the recorder uses.
- Set the days you need to keep. The results give the days you get, the storage your goal needs and drive layouts that reach it.
How the CCTV storage calculation works
A camera writes its bitrate to the drive every second it records. One camera at 1 Mbps for a day is 1 × 86,400 seconds ÷ 8 bits per byte ÷ 1,000 = 10.8 GB. The calculator works that out per group, adds the groups and divides the usable space by the total:
GB a day = sum of (Mbps × share of the day recorded × 10.8 GB × cameras)
days kept = usable GB ÷ GB a day
It is the same formula as our guide to how long security camera recordings last, worked for several groups at once. The constants behind it:
- Example bitrates. At 15 frames per second for a moderately busy scene with H.264: 1080p 3 Mbps, 4MP 5 Mbps, 4K 8 Mbps. H.265 is half, from the published comparison of the two codecs, which found H.265 matched H.264 quality at about 50 percent less bitrate on average.
- Frame rate. Above 15 fps the bitrate scales with the frame rate, so 30 fps doubles it; real streams rise by less, so the answer leans cautious. Below 15 fps the 15 fps figure is kept.
- Drive size. Decimal terabytes, 1 TB = 1,000 GB, as drive makers count. A menu that counts in binary units, as defined in IEC 80000-13, shows about 9 percent less for the same drive.
- Layout. Single drives add up. A mirror keeps half the raw space, RAID 5 gives one drive of space to parity and RAID 6 gives two.
Worked example: a 12 camera walk-up
The walk-up example: 4 entrance cameras at 4MP with H.265 recording all day, and 8 hall cameras at 1080p with H.265 on motion for a quarter of the day, on two 4 TB drives, mirrored.
- Entrances: 2.5 Mbps × 10.8 = 27.0 GB a camera, × 4 = 108.0 GB a day.
- Halls: 1.5 Mbps × 25 percent = 0.375 Mbps on average, × 10.8 = 4.05 GB a camera, × 8 = 32.4 GB a day.
- All 12 cameras: 108.0 + 32.4 = 140.4 GB a day.
- Two 4 TB drives mirrored hold 4,000 GB of video: 4,000 ÷ 140.4 = 28.5 days, short of a 30 day goal.
- Thirty days needs 140.4 × 30 = 4,212 GB. Two 6 TB drives mirrored give 6,000 GB, about 42.7 days.
Typical storage per camera per day
| Camera | Codec | Example bitrate | Storage a day |
|---|---|---|---|
| 1080p | H.264 | 3 Mbps | 32.4 GB |
| 1080p | H.265 | 1.5 Mbps | 16.2 GB |
| 4MP | H.264 | 5 Mbps | 54.0 GB |
| 4MP | H.265 | 2.5 Mbps | 27.0 GB |
| 4K | H.264 | 8 Mbps | 86.4 GB |
| 4K | H.265 | 4 Mbps | 43.2 GB |
Common storage sizing mistakes
- Sizing from a quiet day. Rain, night grain and a busy street raise the bitrate just when incidents rise. Use the busy day margin, or read your recorder's figure on a busy day.
- Counting raw space in a mirror or RAID. Two 8 TB drives mirrored hold 8 TB of video, not 16.
- Treating motion recording as free. Headlights, rain and swaying trees can trigger it all night. Check the real share of the day after a week.
- Forgetting the maximum retention setting. A recorder set to delete video after 30 days keeps 30, even with room for more. The shorter limit wins.
Security camera storage questions
How much storage do I need for 30 days of security camera footage?
Multiply what your cameras write a day by 30. Eight 4MP cameras on H.265 at an example 2.5 Mbps write 216 GB a day, so 30 days needs 6,480 GB, about 6.5 TB of usable space. A single 8 TB drive holds about 37 days at those settings.
How much storage does a security camera use per day?
One camera recording all day at 1 Mbps writes 10.8 GB. At the example bitrates that is 16.2 GB a day for 1080p with H.265 and 54 GB for 4MP with H.264, at 15 fps. Your recorder shows each camera's real bitrate, which you can enter as your own figure.
How many days will a 4 TB drive record?
It depends on the cameras. Four 1080p cameras on H.265 at an example 1.5 Mbps write 64.8 GB a day, so 4 TB holds about 62 days. Eight 4MP cameras on H.264 at 5 Mbps write 432 GB a day and fill it in about 9 days.
Does H.265 double the recording time?
Close to it on average. In the codec developers' published tests, H.265 matched H.264 picture quality at about half the bitrate, and half the bitrate means about twice the days. The real saving varies with the scene and settings, and the recorder and viewing software must support H.265.
How many terabytes do security cameras use per month?
Multiply the daily figure by 30. The 12 camera walk-up example on this page writes 140.4 GB a day, about 4.2 TB a month. A building with eight 4K cameras on H.264 at 8 Mbps writes 691.2 GB a day, about 20.7 TB a month.
Do mirrored drives or RAID reduce recording time?
Yes. A mirror stores everything twice, so two drives hold the video of one. RAID 5 gives up one drive of space for parity and RAID 6 two, in exchange for surviving a failed drive. The calculator counts only the usable space.
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