Two Counting Systems, One Byte
The byte itself is never in dispute — a byte is 8 bits everywhere. The split is purely about what "giga" multiplies. Humans standardized on powers of ten centuries ago (kilo = 1,000, mega = 1,000,000), and the international unit system applies that to bytes exactly as it does to grams and meters. Computers, though, address memory in powers of two, and 2¹⁰ = 1,024 sits temptingly close to 1,000 — so early computing borrowed the metric names for binary quantities and called 1,024 bytes a "kilobyte." Close enough, everyone shrugged, and a 2.4% rounding error was born.
The problem is that the error compounds at every prefix step: 1,024² is 4.9% past a million, and 1,024³ is 7.4% past a billion. By gigabyte scale the "close enough" gap is large enough to see on every drive you buy — and the two meanings of "GB" had become genuinely ambiguous. That ambiguity, not any missing storage, is what the GiB unit was invented to fix.
Who Uses Which — the Full Table
Which software and hardware uses decimal gigabytes versus binary gibibytes | Where you see the number | Counts in | What that means |
|---|
| Drive & SSD boxes, spec sheets | Decimal (GB) | A "1 TB" drive is 1,000,000,000,000 bytes — accurate and standards-compliant |
| Windows File Explorer | Binary math, "GB" label | Divides by 1,024³ but keeps the GB label — the source of most confusion |
| macOS (since 10.6, 2009) | Decimal (GB) | Agrees with the box: 1 TB drive shows as 1 TB |
| Linux tools | Mixed | ls -h and many utilities are binary; some report GiB labels correctly, some say GB |
| RAM / memory modules | Binary by nature | "16 GB" RAM is physically 16 GiB — hardware is addressed in powers of two |
| Steam & many game installers | Binary math | Download sizes computed in 1,024s — pair with our download calculator’s GiB mode |
| Cloud storage plans (Google, iCloud…) | Decimal (GB/TB) | A 2 TB plan is 2×10¹² bytes, decimally counted |
The practical rule that falls out of the table: storage you buy is decimal, memory you install is binary, and Windows reports storage in binary with the wrong label. When a number matters — an upload limit, a backup target, a "will it fit" question — check which dialect produced it before comparing. The same trap exists one level down between MB and GB, and at drive scale in the GB to TB converter, which shows the Windows readout for every size.
How We Got Two Units (the 1998 Fix)
For computing's first decades, "kilobyte" meant 1,024 bytes to programmers and 1,000 to everyone else, and the ambiguity was tolerable because the gap was 2.4% and lawsuits were cheap. As capacities hit gigabyte scale in the late 1990s the gap widened to 7.4%, drive buyers started noticing "missing" space, and standards bodies stepped in: in 1998 the IEC introduced dedicated binary prefixes — kibi (Ki), mebi (Mi), gibi (Gi), tebi (Ti) — so that binary quantities could finally have their own names. The scheme now lives in IEC 80000-13, and NIST's guidance is blunt: metric prefixes are powers of ten, full stop; powers of 1,024 get the -bi names.
Adoption has been lopsided ever since. Standards bodies, Linux kernel documentation, and technical writing moved to KiB/MiB/GiB; consumer software mostly didn't, and Windows' binary-math-with-GB-label remains the most visible holdout. That's why this page exists — and why our tools always state which system a number uses rather than assuming you'll guess. The same disambiguation habit matters even more for speeds, where Mbps vs MB/s hides an 8× gap rather than a 7.4% one.
The Gap Grows With Scale
Each prefix step multiplies by 1,000 on one side and 1,024 on the other, so the disagreement compounds — small at kilobyte scale, a full eighth by petabyte scale:
Percentage difference between decimal and binary units at each prefix level | Pair | Decimal unit | Binary unit | Binary is bigger by |
|---|
| KB / KiB | 1,000 B | 1,024 B | 2.4% |
| MB / MiB | 1,000² B | 1,024² B | 4.9% |
| GB / GiB | 1,000³ B | 1,024³ B | 7.4% |
| TB / TiB | 1,000⁴ B | 1,024⁴ B | 10.0% |
| PB / PiB | 1,000⁵ B | 1,024⁵ B | 12.6% |
This is why the "missing space" complaint gets louder every hardware generation: a 1 TB drive "loses" 69 GB of label, an 8 TB drive "loses" over 700, and a petabyte array misplaces an eighth of itself — all without a single byte going anywhere. The bigger the drive you buy, the more this page's distinction is worth remembering.
