# RAID Capacity Calculator

URL: https://speedycalculator.com/calculators/other/raid/
Last updated: 2026-10-25

> The RAID calculator shows usable storage capacity and fault tolerance for RAID 0, 1, 5, 6 and 10 arrays from the number of drives and drive size.

## Inputs

- Number of drives
- Drive size (TB, GB)
- RAID level

## Results

- Usable capacity
- Storage efficiency
- Drive failures tolerated

## Formula

```
RAID 0: n × size; RAID 1: size; RAID 5: (n − 1) × size; RAID 6: (n − 2) × size; RAID 10: n ÷ 2 × size
```

## Explanation

RAID trades raw capacity for redundancy. RAID 5 survives one drive failure; RAID 6 survives two.

### How to use the RAID Capacity Calculator

- **Number of drives**
- **Drive size**
- **RAID level**

Results update as you type, and every field accepts the units shown in its menu.

### How it works

Usable capacity depends on how many drives’ worth of space is used for parity or mirroring.

### Inputs explained

FieldWhat to enterNumber of drivesA numberDrive sizeUnits: TB, GBRAID levelChoose one: RAID 0 (striping), RAID 1 (mirroring), RAID 5 (single parity), RAID 6 (double parity) …

### Example values

How the main result changes when **Number of drives** changes and everything else stays at the example values above:

Number of drivesUsable capacity (TB)28316424532640856

## Worked example

Inputs — Number of drives: 4; Drive size: 8 TB; RAID level: RAID 5 (single parity).

Results — **Usable capacity = 24 TB**; Storage efficiency = 75 %; Drive failures tolerated = 1.

## FAQ

**Is RAID a backup?**
No; it protects against drive failure, not deletion, ransomware or fire.

**Why does my OS show less space?**
Drives use decimal TB while operating systems often show binary TiB.

**What formula does the RAID Capacity Calculator use?**
RAID 0: n × size; RAID 1: size; RAID 5: (n − 1) × size; RAID 6: (n − 2) × size; RAID 10: n ÷ 2 × size.