How this calculator works
Enter drive count, drive size (tb), parity drives. CalcStack applies the displayed formula and reports each intermediate planning value with the units shown.
Formula / method
Usable capacity = (drive count − parity drives) × drive size
Worked example
Eight 4 TB drives with two parity drives provide 24 TB usable capacity.
Assumptions and limitations
Drives have identical decimal capacities and the selected parity count is reserved fully.
Filesystem overhead, hot spares, rebuild space, vendor TB/TiB reporting and replication are excluded.