Storage Unit Converter
Why your 1 TB drive says 931 GB.
Convert Storage Unit. Why your 1 TB drive says 931 GB. Names the misconception directly.
In binary units
931.32 GiB
1,000 GB decimal · a 6.9% gap
This is why a 1 TB drive shows as 931 GB. Drive manufacturers use decimal prefixes, where 1 TB is 10¹² bytes; operating systems have historically reported binary quantities — 2⁴⁰ bytes — while labelling them TB. Neither is lying, and the gap is 9.95% at terabyte scale. The IEC introduced KiB, MiB, GiB and TiB in 1998 specifically to end this, and adoption has been patchy. Linux and macOS now generally use decimal for storage; Windows still reports binary with decimal labels. The discrepancy compounds with size: 7.4% at gigabyte scale, 9.95% at terabyte, and over 12% at petabyte. On a large array that is a meaningful amount of apparently missing space.
How the Storage Unit Converter works
Storage in both decimal and binary prefixes, labelled correctly. Drive makers use decimal and operating systems have historically reported binary — a 7 to 12% gap that accounts for most confusion about missing disk space.
Also known as: why is my hard drive smaller than advertised · gb versus gib · 1tb is how many gb · bytes to gigabytes converter
Frequently asked questions
Why does my 1 TB drive show as 931 GB?
The manufacturer used decimal — 1 TB is 10¹² bytes — and the operating system reported the binary equivalent while labelling it GB. Both describe the same drive; the units differ by 9.95% at that scale.
What is the difference between GB and GiB?
A GB is 10⁹ bytes and a GiB is 2³⁰, which is 1,073,741,824 — about 7.4% more. The IEC introduced the binary prefixes in 1998 specifically to end the ambiguity.
Who uses which?
Drive and network hardware makers use decimal. Windows reports binary with decimal labels; Linux and macOS now generally use decimal for storage. RAM is always quoted in binary, because of how addressing works.
Does the gap get worse with size?
Yes — 2.4% at kilobyte scale, 7.4% at gigabyte, 9.95% at terabyte and over 12% at petabyte. On a large array that is a substantial amount of apparently missing space.
Am I being cheated by drive manufacturers?
No. Decimal prefixes are the SI standard and mean exactly what they say. The confusion comes from software labelling binary quantities with decimal names.
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