Planning a storage array means deciding how much usable capacity, fault tolerance, and drive cost you can accept before buying hardware. A RAID Calculator answers all three at once: choose a RAID Type, enter Drive Capacity and Drive Cost, set Drives per RAID, and add RAID Groups if you want totals. Home NAS builders, photographers, and IT administrators use it to compare layouts without spreadsheets.
The tool also makes the redundancy bill explicit, showing how much raw storage each layout sacrifices for protection. The Drive Cost field does the same for your budget.
Each level has its own formula. RAID 0 stripes data and yields n times the drive size, while RAID 1 mirrors and yields just one drive size. RAID 5 adds parity and follows the n-1 drives rule, and RAID 10 stripes mirrors for an n/2 result, half the raw total.
A quick worked example uses four 4-terabyte drives at 100 dollars each. RAID 0 gives 16 terabytes usable, RAID 5 gives 12, and RAID 10 gives 8. RAID 1 leaves only 4. Every option still costs 400 dollars in disks, so the calculator shows how differently the same money pays out.
Pick the RAID Type first, then enter Drive Capacity exactly as labeled, since market terabytes shift results by a few percent. Enter Drive Cost per disk, the number of Drives per RAID, and the count of RAID Groups, then press Calculate.
Remember two classic pitfalls: RAID 5 needs at least three drives, and RAID 10 needs an even number, since drives work in mirrored pairs. Treat the array as redundancy for hardware failure, not as a backup plan. Cost per usable terabyte is the honest comparison, where RAID 5 usually wins for archives and RAID 10 wins for databases.
RAID 5 spends one drive per group on parity, so usable space follows the n-1 drives rule. Four 4-terabyte drives therefore provide 12 terabytes usable, not the full 16.
RAID 10 mirrors data across pairs of drives, so usable capacity is n/2 of the raw total. Eight 2-terabyte drives deliver 8 terabytes usable rather than 16.
RAID 1, 5, and 10 survive losing one or more drives, but RAID 0 does not, since a single drive failure destroys the entire striped array.
No, RAID handles hardware failure only. Deleted files, ransomware encryption, or controller damage replicate across the array, so pair it with an off-device or offsite backup.
Enter the price per disk in the Drive Cost field, and the tool multiplies by Drives per RAID and RAID Groups. Four 100-dollar drives, for instance, total 400 dollars.