ucUnitCloudInternational unit matrix

Mistake guide

Treating GB and GiB as the same

A 1 TB drive stores 1 TB of data.

01Assumption

A 1 TB drive stores 1 TB of data.

02Actually

1 TB is 10¹² bytes, i.e. 1000 GB. Operating systems display the same drive in GiB: 1 TB ≈ 931 GiB. At this step the difference between decimal and binary notation is about 7.4 %.

03Why

Manufacturers count in decimal because it yields larger numbers, operating systems count in binary because memory is organised in powers of two. Both sides are right — just not in the same unit.

04Check

Check the prefix: GB, MB and TB are decimal, GiB, MiB and TiB are binary. If a capacity looks smaller than advertised, first check whether system and packaging use different prefixes before assuming a defect.

Matching conversions

Gigabyte to GibibyteGB → GiBDataGibibyte to GigabyteGiB → GBDataTerabyte to TebibyteTB → TiBDataMegabyte to GibibyteMB → GiBData

Matching tables

TableData volumes: binary versus decimal

Unit family: Data

Sources

IEC 80000-13Binary prefixes KiB, MiB, GiB, TiB against the decimal SI prefixes.BIPM SI BrochureSI base units, prefixes and official SI context.
When not to use

Do not use as the sole basis for official, medical, safety-critical or contractual decisions.

Citation

Citation note: UnitCloud, mistake guide, sources reviewed: September 2026. Source basis: IEC 80000-13 · BIPM SI Brochure.