Disk IOPS Calculator
Storage performance is described by IOPS (operations per second), block size and throughput. This calculator links all three: enter IOPS and block size to get throughput in MB/s, and enter a spinning disk's RPM and seek time to estimate its random-I/O IOPS from rotational and seek latency.
IOPS and throughput formulas
Throughput (KiB/s) = IOPS * block size (KiB)
Throughput (MiB/s) = throughput KiB/s / 1,024
Avg rotational latency (ms) = 30,000 / RPM
Estimated IOPS = 1,000 / (seek time + avg rotational latency)
Average rotational latency is half a revolution: one revolution takes 60,000 / RPM ms, so the average wait is 30,000 / RPM ms. The spinning-disk IOPS estimate is for random access; sequential workloads are far faster.
Worked example: a 7,200 RPM disk
Average rotational latency = 30,000 / 7,200 = 4.17 ms. With a 4 ms seek, total per-I/O time is about 8.17 ms, so estimated random IOPS = 1,000 / 8.17 = about 122. Separately, 1,000 IOPS at a 64 KiB block is 64,000 KiB/s = 62.50 MiB/s.
Disk IOPS: frequently asked questions
What is IOPS?
IOPS stands for input/output operations per second: the number of read or write requests a storage device completes each second. Together with the block size of each operation it determines throughput. IOPS is a common way to size and compare storage performance.
How are IOPS and throughput related?
Throughput equals IOPS multiplied by block size. So 1,000 IOPS at a 64 KiB block size is 1,000 times 64 = 64,000 KiB/s, which is about 62.5 MiB/s. Rearranged, IOPS equals throughput divided by block size.
How do you estimate IOPS for a spinning hard drive?
For a rotational disk the time per random I/O is roughly the average seek time plus the average rotational latency. Average rotational latency is half the time for one revolution: 30,000 divided by the disk RPM in milliseconds. IOPS is then 1,000 divided by that total millisecond figure.
Does this apply to SSDs?
The throughput conversion applies to any device. The rotational latency model is for spinning disks only; solid-state drives have no seek or rotation, so quote their IOPS from the manufacturer specification and use the throughput conversion.
Sources and notes
- The throughput relation (throughput = IOPS times block size) and the rotational-latency model (half a revolution) are standard storage-performance definitions.
- Seek time and RPM are device specifications; enter the values from your drive's datasheet.
Reviewed by the CalculatorHub team, edited by James Graham, 19 June 2026. See our methodology.