Storage Units Calculator
Convert KB, MB, GB and TB — in both decimal (1000) and binary (1024) systems — and see why a 1 TB drive shows ~931 GiB.
How it works
decimal: 1 KB = 1000 B, 1 MB = 1000², 1 GB = 1000³, 1 TB = 1000⁴ · binary: steps of 1024 (KiB, MiB, GiB, TiB)
Two unit systems share the same names, which causes endless confusion. Storage vendors use decimal prefixes, where each step is ×1000; operating systems and RAM use binary steps of ×1024, properly written KiB/MiB/GiB/TiB. The gap compounds with each tier: 2.4% at kilobytes, 4.9% at megabytes, 6.9% at gigabytes and 9.1% at terabytes. This calculator treats your input as decimal (label-on-the-box) units and shows both readings.
Worked example
500 GB decimal is 500,000,000,000 bytes. In binary units that is 500×10⁹ ÷ 1024³ = 465.66 GiB — which is exactly what a fresh "500 GB" drive reports, minus a little filesystem overhead.
Frequently asked questions
Did the store cheat me out of 69 GB on my 1 TB drive?
No — you got the full 10¹² bytes. The operating system divides by 1024³ and shows ~931 "GB" (really GiB). Same bytes, different ruler. Formatting overhead then takes a further slice.
Which system should I use?
Decimal for drives, network transfer and anything a vendor labels; binary for RAM and whatever your OS reports. When precision matters, spell it out in bytes — that number is unambiguous.
Why 1024 in the first place?
Computers address memory in powers of two, and 2¹⁰ = 1024 was close enough to 1000 that early engineers borrowed the metric prefixes. The IEC coined KiB/MiB/GiB in 1998 to untangle the two, but adoption is still patchy.
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This calculator is for educational purposes. Double-check important results before acting on them.