About Synology RAID Calculator
A free, accurate RAID storage planning tool for Synology NAS users. No sign-ups, no ads, no guesswork.
Why We Built This Calculator
Most people shopping for a Synology NAS make the same mistake: they assume the total drive capacity is what they'll get to use. Buy four 4TB drives and expect 16TB. But in RAID 5, you only get 12TB. In RAID 6, just 8TB. These aren't small discrepancies; they affect whether you buy a 4-bay or 6-bay unit, and whether your storage budget goes far enough.
We built this calculator because Synology's own tool, while accurate for mixed-drive SHR arrays, requires navigating their website and doesn't make it easy to compare configurations side by side. We wanted a panel that loads instantly, shows all the numbers you need, and works on mobile without friction.
The site is completely free. There are no accounts, no subscription tiers, no ads cluttering the readout. You get the numbers, and you make the decision.
What the Calculator Covers
All seven RAID types Synology supports: RAID 0, 1, 5, 6, 10, SHR, and SHR-2. Results include usable storage, raw storage, storage efficiency, and drive fault tolerance. Minimum drive requirements are validated. You'll get an error if you try to configure RAID 5 with two drives.
How We Verify Accuracy
Our formulas come from Synology's DiskStation Manager (DSM) documentation and the Storage Networking Industry Association (SNIA) RAID specification. We cross-check results against Synology's own calculator for standard RAID configurations.
Editorial Process
Every piece of content on this site is written by storage professionals with hands-on NAS experience. We cite industry standards by name, use real drive sizes and real capacity numbers, and verify all claims before publishing.
Who Uses This Tool
Home NAS users planning their first Synology setup are the most common visitors. They're trying to decide between a DS223j with 2 drives and a DS923+ with 4, or figuring out whether RAID 5 or SHR makes more sense for their drive sizes.
IT admins and managed service providers use it for quick capacity planning during client consultations. Comparing a 4-bay RAID 5 array against a 6-bay RAID 6 configuration takes seconds rather than pulling up a spreadsheet.
Homelab enthusiasts running Synology alongside TrueNAS or unRAID setups use it to sanity-check storage expansion plans. And Synology shoppers use it before purchasing drives to confirm that their chosen configuration actually meets their storage targets.
What This Calculator Doesn't Cover
Mixed-drive SHR calculations are approximate. Synology's SHR algorithm allocates capacity across unequal drives in ways that aren't publicly documented in full. For exact figures on mixed arrays, use Synology's official RAID calculator.
Drive capacity shown is in TB (decimal terabytes), which is how drive manufacturers and Synology DSM report storage. Actual formatted capacity in a file system is slightly lower due to binary vs. decimal conversion. A 4TB drive formats to approximately 3.63 TiB. This doesn't affect RAID calculations, but it's worth knowing when comparing to what your OS reports.
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Found an error in the calculations, want to report an outdated formula, or have a suggestion? We read every message.
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