Data Storage Unit Converter (Decimal vs. Binary)
Convert between bytes, decimal units (KB/MB/GB/TB) and binary units (KiB/MiB/GiB/TiB) — the exact reason a '1 TB' drive shows up as ~931 GB in your OS.
- Converted value
- 931.322575
How it works
Storage units come in two competing families that both use similar-looking prefixes for different bases. Decimal (SI) units step by powers of 1000: 1 KB = 1000 B, 1 MB = 1000² B, and so on. Binary (IEC) units step by powers of 1024: 1 KiB = 1024 B, 1 MiB = 1024² B, and so on. This calculator converts to bytes first using whichever base the source unit implies, then to the target unit's base.
This is exactly why a drive marketed as '1 TB' (the manufacturer's decimal definition, 10¹² bytes) shows up as roughly 931 GiB in an operating system that reports binary units — both figures are mathematically correct, they're just counting with a different base. Try converting 1 TB to GiB below to see that exact gap.
FAQ
Why does my new drive show less storage than advertised?
Drive manufacturers label capacity in decimal units (1 TB = 1,000,000,000,000 bytes), which is the SI-standard meaning of the prefix. Most operating systems display free space in binary units instead (dividing by 1024 at each step) but often still label them 'GB' or 'TB' rather than the more precise 'GiB'/'TiB' — so the same number of physical bytes shows a smaller number under the binary convention. No storage is actually missing.
Which convention is 'correct'?
Both are internally consistent; they're just different, equally valid conventions. Network speeds and storage marketing almost always use decimal (1 KB = 1000 B), while memory (RAM) and many operating systems' file size displays use binary (1 KiB = 1024 B), since binary sizes align naturally with how memory addressing works.