RAID Capacity Calculator

Enter the number of disks, disk size, and RAID level to quickly estimate the usable capacity of your RAID array.

This free RAID calculator supports RAID 0, RAID 1, RAID 5, RAID 6, and RAID 10, and is useful for planning NAS, server, and custom PC storage setups.

Calculate RAID Capacity

RAID Type Number of Disks Disk Size (TB)

* This is a simplified estimate assuming identical disk sizes.
* Actual usable capacity may vary slightly because of filesystem overhead and manufacturer definitions.

Quick RAID Capacity Overview

RAID 0: Uses the full capacity of all disks, but provides no redundancy
RAID 1: Uses the capacity of one disk, because data is mirrored
RAID 5: Uses the total minus one disk for parity
RAID 6: Uses the total minus two disks for parity
RAID 10: Uses half of the total raw capacity

Example: Four 8TB Disks

Here is how usable capacity changes with the RAID level:

RAID 0: 32TB
RAID 1: 8TB
RAID 5: 24TB
RAID 6: 16TB
RAID 10: 16TB

Which RAID Level Should You Choose?

Maximize usable capacity: RAID 0 or RAID 5
Prioritize safety: RAID 1 or RAID 6
Balanced option: RAID 5
Performance and redundancy: RAID 10

The best RAID level depends on what matters more in your setup: storage efficiency, fault tolerance, or performance.

How RAID Capacity Is Calculated

Usable RAID capacity depends on the RAID level:

RAID 0: Number of disks × disk size
RAID 1: Capacity of one disk
RAID 5: (Number of disks - 1) × disk size
RAID 6: (Number of disks - 2) × disk size
RAID 10: (Number of disks / 2) × disk size

Example: 4 disks × 8TB in RAID 5 → (4 - 1) × 8 = 24TB

Next Step: Choose Your Hardware

Now that you know your RAID configuration, it's time to choose the right NAS and hard drives.

Beginner setup (RAID 1 / 2 drives)
Balanced setup (RAID 5 / 4 drives)
High safety setup (RAID 6)

👉 View Recommended NAS & HDD Setup

RAID Is Not a Backup

RAID can improve fault tolerance against disk failure, but it does not protect your data from accidental deletion, malware, ransomware, or disasters.

Important data should always be backed up separately.

Learn How RAID Capacity Works →

Learn More About RAID

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