Storage Calculator
Three storage tools in one: what a drive really holds, the capacity of a multi drive array, and how much video or how many installs fit.
How to use the Storage Calculator
- Enter an advertised drive size to see the space your operating system reports.
- Enter the number and size of drives and choose a layout to see array capacity and fault tolerance.
- Enter free space and a video bitrate or item size to see what fits.
- Leave any block empty to skip it.
How it is calculated
Drive makers count 1 TB as 1,000,000,000,000 bytes. Windows divides by 1,073,741,824 and labels the result GB, so a 1 TB drive shows about 931 GB. The difference is about 6.9% and is not missing space.
RAID 0 gives all drives, RAID 1 gives one drive, RAID 5 loses one drive to parity, RAID 6 loses two, and RAID 10 gives half. Video size per hour is bitrate in Mbps times 0.45 GB. A RAID array is not a backup.
Frequently asked questions
Why does my 1 TB drive show 931 GB?
The maker counts in powers of 10 while Windows counts in powers of 2. The drive holds the full amount it was sold with.
Is RAID a backup?
No. RAID keeps a system running after a drive failure but does not protect against deletion, malware or a failed controller. Keep a separate backup.
How much free space should an SSD keep?
Leaving some space free helps write speed and wear. Many people aim for at least 10 to 20% free.
How do I find my video bitrate?
Check your recording software settings. Bitrate is listed in Mbps or kbps. Divide kbps by 1,000 to get Mbps.