Raid Calculator
Solve raid problems step-by-step with formula explanation and worked examples
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About Raid Calculator
Plan Your Storage with the RAID Calculator
A RAID calculator is a must-have tool for system administrators, IT professionals, and anyone building a storage array. RAID - Redundant Array of Independent Disks - combines multiple physical drives into a logical unit to improve performance, redundancy, or both. But choosing between RAID 0, 1, 5, 6, 10, and other levels involves trade-offs that are not always intuitive. This calculator quantifies those trade-offs so you can make an informed decision before purchasing hardware.
Understanding RAID Levels at a Glance
Each RAID level offers a different balance of usable capacity, fault tolerance, and read/write performance. RAID 0 stripes data across drives for maximum speed and capacity but offers zero redundancy - one drive failure means total data loss. RAID 1 mirrors data for full redundancy but halves your usable space. RAID 5 distributes parity across three or more drives, tolerating a single drive failure while sacrificing only one drive's worth of capacity. RAID 6 adds a second parity block, surviving two simultaneous failures. RAID 10 combines mirroring and striping for both speed and redundancy at the cost of half the total capacity.
The RAID calculator takes the guesswork out of these comparisons. Enter the number of drives, individual drive capacity, and desired RAID level, and it immediately shows you total usable storage, space lost to redundancy, and fault tolerance characteristics.
Why You Should Calculate Before You Build
Drives are expensive, and over-provisioning wastes budget while under-provisioning leads to painful expansion projects later. A server room manager planning a new file server needs to know exactly how many drives of what size to order. A small business owner setting up a NAS for backups wants to maximise usable storage without sacrificing the ability to survive a drive failure. A video production house needs both speed and capacity for editing raw footage. In every case, running the numbers through a RAID calculator first prevents costly mistakes.
How to Use the RAID Calculator
Select the RAID level you are considering. Enter the number of physical drives and the capacity of each drive. The calculator displays the total raw capacity, usable capacity after RAID overhead, storage efficiency as a percentage, and the number of drives that can fail without data loss. Compare multiple RAID levels side by side to see which one best fits your requirements.
For mixed-size drives, some RAID implementations limit usable capacity per drive to the size of the smallest drive. The calculator can model this scenario, showing you how much capacity you waste by mixing a 2 TB drive with several 4 TB drives - a common and costly oversight.
Comparing RAID Levels: A Practical Example
Suppose you have six 4 TB drives. In RAID 0, you get the full 24 TB of usable space, but no fault tolerance. RAID 5 gives you 20 TB with single-drive fault tolerance. RAID 6 gives 16 TB with double-drive fault tolerance. RAID 10 gives 12 TB with excellent performance and the ability to lose one drive per mirrored pair. Seeing these numbers side by side - which this RAID calculator produces instantly - makes the decision far clearer than trying to hold the formulas in your head.
Advanced Considerations
Beyond capacity and fault tolerance, consider rebuild times. Larger drives take longer to rebuild after a failure, and during a rebuild the array is vulnerable. RAID 6 mitigates this risk by tolerating a second failure during rebuild. Hot spares - unused drives standing by for automatic rebuild - add another layer of protection. While this calculator focuses on capacity and redundancy, keep rebuild risk in mind when choosing between RAID 5 and RAID 6 for large-capacity drives.
Browser-Based and Private
The RAID calculator runs entirely in your browser. No installation, no registration, and no data leaves your device. Use it on your phone while browsing drive prices online, or on your workstation while planning a data centre expansion. It is always available, always free, and always fast.
Build Your Array with Confidence
Storage decisions have long-term consequences. Getting the RAID level and drive count right from the start saves money, protects data, and avoids disruptive migrations later. Use this RAID calculator to plan your array with precision and deploy with confidence.