RAID Calculator – Storage, Redundancy & Capacity Estimator
Enter the number of disks, the size of one disk and a RAID level to estimate usable capacity, redundancy and fault tolerance.
Total vs Usable Capacity: What You Actually Get
The gap between total and usable capacity is where most RAID planning goes wrong. In a mirror, half your raw space simply holds a second copy of your data, while parity arrays set aside the equivalent of one or two whole drives to rebuild information after a failure. This tool makes that trade-off clear: a raid 5 calculator result shows a single drive lost to parity, and a raid 6 calculator result shows two, in exchange for surviving more failures. Seeing usable space and overhead together helps you decide whether raw capacity, stronger protection, or a mix of both matters most for your data.
How RAID Levels Affect Speed and Safety
RAID levels also behave very differently under load. Striping spreads reads and writes across every drive for speed, which is why a RAID 0 setup is fast but keeps no safety net, while nested layouts add protection on top. Read the output as a raid performance calculator and raid speed calculator to weigh throughput against redundancy, and remember that parity writes add overhead a simple mirror avoids. Storage speed is only one piece of how a system feels, though. For gaming frame rates your processor and graphics card matter far more, which you can estimate with our FPS Calculator.
How Do You Choose the Right RAID Level?
Choosing a RAID level is about matching risk to workload, not chasing the biggest number. Start with how many simultaneous drive failures you need to survive: RAID 0 protects nothing, mirroring and single parity handle one failed drive, and double parity handles two. Then think about rebuild time, because a large array can take many hours to restore, and a second failure during that window can be fatal to your data. A raid 10 calculator result is popular here, since mirrored stripes rebuild quickly and stay fast, at the cost of usable space. Match drive size, speed, and endurance so the array behaves predictably, and never treat redundancy as a backup, since RAID cannot undo deletion, corruption, or theft. Storage is only part of a healthy build, so keep the rest balanced with our Bottleneck Calculator when planning the whole system.
Before You Build: A Quick RAID Planning Checklist
A little planning prevents expensive mistakes. Before you commit to a level, run through these four questions so your array matches how you actually store and protect data, not just the capacity number on the box.
Set Your Priority
Decide what matters most for this array: maximum capacity, raw speed, or the strongest protection. Naming that priority instantly narrows your choice of level.
Plan the Rebuild
After a drive fails, the array runs unprotected until the replacement rebuilds, which can take hours on large disks. Pick a level with enough headroom to survive that window.
Match Your Drives
An array uses only the capacity of its smallest member, so similar size, speed, and endurance keep performance predictable and avoid wasting larger drives.
Know Your Workload
Large media files, many small writes, and mixed daily use each stress an array differently. Balance capacity efficiency against the write overhead that parity adds.