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Storage Calculator

Difference between units

It's important to understand the difference between decimal units (International System) and binary units (multiples of 1024):

  • 1 KB (kilobyte) = 1000 bytes - Used by hard drive manufacturers
  • 1 KiB (kibibyte) = 1024 bytes - Used by operating systems
  • 1 MB = 1000 KB | 1 MiB = 1024 KiB
  • 1 GB = 1000 MB | 1 GiB = 1024 MiB

This difference explains why a "1TB" hard drive appears as "931 GiB" in Linux.

Why understanding the unit difference matters

Confusion between decimal and binary units is one of the most common sources of errors in system administration. When planning storage capacity, buying disks, or sizing partitions, using the wrong unit can lead to errors of up to 7% in actual available capacity.

Real example: If you need to store 1000 files of 1 GiB each, you need 1 TiB of space. But if you buy a 1 TB (decimal) drive, the actual capacity will be only 0.909 TiB (approximately 931 GiB), not enough for your 1000 files.

In networks and transfers: Internet speeds are measured in bits per second (bps), not bytes. A 1 Gbps connection transfers approximately 119 MiB/s, not 125 MB/s. This difference is crucial when calculating transfer times for backups or migrations.

Frequently Asked Questions

What is the difference between KB and KiB?
Kilobyte (KB) uses the decimal system: 1 KB = 1000 bytes. Kibibyte (KiB) uses the binary system: 1 KiB = 1024 bytes. Hard drive manufacturers use KB/MB/GB (decimal), while operating systems like Linux measure in KiB/MiB/GiB (binary). That's why a 1 TB drive appears as 931 GiB on your system.

Why does my 1TB hard drive only show 931GB in Windows?
This difference is due to the unit system: manufacturers use decimal units (1 TB = 1,000,000,000,000 bytes), while Windows and Linux display capacity in binary units (1 TiB = 1,099,511,627,776 bytes). 1,000,000,000,000 / 1,099,511,627,776 = 0.909 TiB, approximately 931 GiB. It's the same drive, just measured differently.

What storage units exist besides KB, MB, and GB?
Main units: byte (B), kilobyte (KB, 10^3), megabyte (MB, 10^6), gigabyte (GB, 10^9), terabyte (TB, 10^12), petabyte (PB, 10^15), exabyte (EB, 10^18). Their binary equivalents: kibibyte (KiB, 2^10), mebibyte (MiB, 2^20), gibibyte (GiB, 2^30), tebibyte (TiB, 2^40), pebibyte (PiB, 2^50), exbibyte (EiB, 2^60).

How do I easily convert between GiB and GB?
Use our storage calculator: enter the amount and select source and target units. General formula: 1 GiB = 1.0737 GB, 1 GB = 0.9313 GiB. For quick conversion, multiply GB by 0.9313 to get GiB, or GiB by 1.0737 to get GB.

What units are used for RAM and why?
RAM is always measured in binary units (MiB, GiB) because memory modules have capacities based on powers of 2: 1 GiB = 1024 MiB. This is due to the binary nature of integrated circuits. So 16 GB of RAM is actually 16 GiB (16,384 MiB), not 16,000 MB.

How does the decimal vs binary unit difference affect disk partitioning?
When partitioning with fdisk, gdisk, or parted, some programs use decimal and others binary units. Modern fdisk uses sectors (512 bytes), while graphical tools may display in GB or GiB. A common mistake is creating a "100 GB" partition when you actually need "100 GiB", resulting in a partition 7% smaller than expected.
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