Data Size Converter

Type any data size — 12.5 MB, 1024 KiB, 8 Gbit — and read every other unit at once. Toggle between the SI convention (1 KB = 1000 B, used by hard drive vendors and network speeds) and the IEC convention (1 KiB = 1024 B, used by most operating systems). Source and output can be in different conventions so you can see exactly how much a "1 TB" drive loses when the OS reports it in TiB. Bulk mode for many inputs at once. Pure math in your browser — nothing is uploaded.

Source convention

Interpret input as
Output convention
Decimals
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In every unit

UnitValueBytes (exact)
Type a size above.
SI vs IEC — what's the difference and why it matters

The number on a 1 TB hard drive is in SI: it's 1,000,000,000,000 bytes. The number your operating system reports for the same drive (after formatting and after it leaves some space for housekeeping) is in IEC, so it shows as roughly 931 GiB. The "missing" ~7% is the gap between the two conventions. The same applies to KB / KiB (~2.4% gap), MB / MiB, GB / GiB, and so on.

"bit" is always a single binary digit (a 0 or a 1). It is the only unit that appears inside both conventions at the same scale: 1 byte = 8 bits in both SI and IEC, because the "thousand vs 1024" prefix only applies to multiples of the byte.

This tool renders every unit with the same precision, so you can eyeball the gap directly — pick a value in one convention, output it in the other, and the cross-system gap is the answer.