How to Use RAID Calculator
The RAID Calculator gives you instant storage estimates for any RAID configuration:
- Select RAID level — choose from RAID 0, RAID 1, RAID 5, RAID 6, or RAID 10 in the dropdown. The RAID Calculator will automatically apply the correct capacity formula for that level.
- Enter disk count — type the number of hard drives or SSDs in your array.
- Enter disk size — input the capacity of each individual disk in GB (e.g. 2000 for a 2 TB drive).
- Read the results — the RAID Calculator instantly shows raw capacity, usable capacity, redundancy overhead, utilization rate, and the maximum number of disk failures your array can tolerate.
The RAID Calculator recalculates on every change, so you can compare different RAID levels and disk configurations side by side without re-entering data.
Formula & Theory — RAID Calculator
The RAID Calculator applies the industry-standard formulas for each RAID level. Given $n$ disks each with capacity $C$:
Raw Capacity = n × C
RAID 0 Usable = n × C (no redundancy)
RAID 1 Usable = C (full mirror)
RAID 5 Usable = (n − 1) × C (single parity disk equivalent)
RAID 6 Usable = (n − 2) × C (double parity)
RAID 10 Usable = (n / 2) × C (striped mirrors)
Redundancy Overhead = Raw − Usable
Utilization Rate = Usable / Raw × 100%
| Symbol | Meaning |
|---|---|
| n | Number of disks |
| C | Capacity per disk (GB) |
Maximum Tolerable Failures
| RAID Level | Max Disk Failures |
|---|---|
| RAID 0 | 0 |
| RAID 1 | n − 1 |
| RAID 5 | 1 |
| RAID 6 | 2 |
| RAID 10 | n / 2 (one per mirrored pair) |
The RAID Calculator displays this value so you can immediately understand the resilience of your chosen configuration.
Use Cases for RAID Calculator
The RAID Calculator is useful in a wide range of storage planning scenarios:
- NAS planning — before buying drives for a Synology, QNAP, or DIY NAS, use the RAID Calculator to compare usable capacity across RAID levels and find the best balance of space and redundancy.
- Server storage design — system administrators can use the RAID Calculator to size RAID arrays for databases, virtual machines, or file servers before purchasing hardware.
- Budget estimation — the RAID Calculator shows exactly how much raw capacity you need to achieve a target usable capacity, helping you estimate drive costs accurately.
- Evaluating redundancy trade-offs — compare RAID 5 vs RAID 6 vs RAID 10 side by side to decide how much redundancy your workload requires.
- Home lab and hobbyist builds — whether you are building a media server or a personal backup vault, the RAID Calculator helps you avoid buying too few or too many drives.
- Learning RAID concepts — students and IT professionals studying storage fundamentals can use the RAID Calculator to verify their understanding of each level's capacity formula.
The RAID Calculator is the fastest way to turn your disk count and size into a clear picture of usable storage, redundancy, and fault tolerance — without manually working through the formulas.