Know your array's real IOPS before you buy it.
Enter your disk count, per-disk IOPS rating, RAID level, and read/write mix — get raw and functional IOPS with the exact math behind every number.
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Storage array IOPS calculator
All values are computed instantly in your browser — nothing is sent to a server.
The formula used
| RAID level | Write penalty |
|---|---|
| RAID 0 | ×1 |
| RAID 1 / 10 | ×2 |
| RAID 5 | ×4 |
| RAID 6 | ×6 |
Your array's IOPS result
Built for accurate storage sizing
Every result is computed with the real RAID write-penalty formula used across the storage industry.
Real-time validation
Inputs are checked as you type — disk count, IOPS rating, and read/write split are all range-checked before you can submit.
Five RAID levels
RAID 0, RAID 1/10, RAID 5, RAID 6, and JBOD, each with its correct write-penalty multiplier applied automatically.
Copy & download results
Export your calculation as plain text, copy it to the clipboard, or share the tool link directly with your team.
Dark & light themes
Switch instantly between a low-glare dark interface and a bright light theme, saved for your next visit.
Fully client-side
All math runs in your browser. Your disk configuration and results are never transmitted to any server.
Mobile friendly
A responsive layout that fits any screen width with no horizontal scrolling, from phones to ultrawide monitors.
How the IOPS calculator works
Four inputs, one accurate result.
Enter disk details
Provide the number of disks in your array and the rated IOPS of a single disk from its datasheet.
Choose your RAID level
Select RAID 0, 1/10, 5, 6, or JBOD. The correct write-penalty multiplier is applied automatically.
Set your read/write mix
Enter the percentage split of read versus write operations that matches your real workload.
Read your functional IOPS
Get raw IOPS, read IOPS, usable write IOPS, and total functional IOPS — copy, download, or share the result.
What is an IOPS calculator, and how do you use one?
An IOPS calculator estimates how many input/output operations per second a storage array can realistically deliver to an application. Raw IOPS, the number printed on a disk's datasheet multiplied by how many disks you own, only tells part of the story. Once disks are grouped into a RAID array, every write operation triggers extra work: RAID 1 duplicates each write to a mirror, while RAID 5 and RAID 6 must read and rewrite parity blocks across the array. That extra work is called the write penalty, and it silently eats into the IOPS your applications actually get to use.
To use the calculator above, start with the number of disks in your array and the IOPS rating of a single disk, usually available on the manufacturer's datasheet or benchmark report. Typical figures are 75–100 IOPS for a 7,200 RPM SATA drive, 125–150 IOPS for a 10,000 RPM SAS drive, and anywhere from 10,000 to well over 200,000 IOPS for SATA and NVMe SSDs. Next, choose the RAID level your array uses, since this determines the write penalty applied in the formula. Finally, estimate the read/write mix of your workload; a transactional database might run 70% reads and 30% writes, while a backup target could be nearly all writes.
A worked example
Take an 8-disk array where each disk is rated at 150 IOPS, configured as RAID 5, serving a workload that is 70% reads and 30% writes. Raw IOPS is 8 × 150 = 1,200. Read IOPS is 1,200 × 70% = 840. Write IOPS before the penalty is 1,200 × 30% = 360, and RAID 5's write penalty of 4 reduces that to 360 ÷ 4 = 90 usable write IOPS. Functional IOPS, the number that actually matters for sizing, comes to 840 + 90 = 930 — well under the 1,200 raw figure most vendors quote.
This gap between raw and functional IOPS is why undersized RAID 5 and RAID 6 arrays frequently bottleneck write-heavy databases, and why architects lean toward RAID 10 or all-flash arrays for latency-sensitive workloads. Running the numbers before purchasing hardware, rather than after a slow rollout, is the entire purpose of this tool.
Frequently asked questions
IOPS stands for Input/Output Operations Per Second. It measures how many read and write requests a storage device or array can process every second, and is a core metric for sizing databases, virtual machines, and other latency-sensitive workloads.
Functional IOPS equals raw IOPS multiplied by the read percentage, plus raw IOPS multiplied by the write percentage divided by the RAID write penalty. The write penalty is 1 for RAID 0, 2 for RAID 1/10, 4 for RAID 5, and 6 for RAID 6.
Parity-based RAID levels must read and rewrite parity blocks on every write, so each logical write generates several physical disk operations. RAID 5 has a write penalty of 4 and RAID 6 has a write penalty of 6, which reduces the usable write IOPS available to applications.
A 7,200 RPM SATA HDD typically delivers 75–100 IOPS, a 10,000 RPM SAS HDD around 125–150 IOPS, a 15,000 RPM SAS HDD around 175–210 IOPS, a SATA SSD roughly 10,000–50,000 IOPS, and an NVMe SSD can exceed 200,000 to over a million IOPS depending on the model.
Yes. You enter the percentage of read and write operations for your workload, and the calculator applies the RAID write penalty only to the write portion, since reads are not affected by parity or mirroring overhead.
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