Reference table

Data volumes: binary versus decimal

Drive manufacturers count in decimal (GB = 10⁹ bytes), operating systems count in binary (GiB = 2³⁰ bytes). That is why a “1 TB drive” shows less than 1 TB in the system. The deviation grows with every step.

Data volumes: binary versus decimal
Binary prefixIn bytesCorresponding decimalDeviation
1 KiB1,024 B1.024 KB2.4 %
1 MiB1,048,576 B1.048576 MB4.8576 %
1 GiB1,073,741,824 B1.073741824 GB7.3742 %
1 TiB1,099,511,627,776 B1.0995116278 TB9.9512 %
1 PiB1.1259e15 B1.1258999068 PB12.59 %

Each row contrasts a binary prefix with the equivalent decimal prefix: 1 GiB is 1.073741824 GB, not 1 GB. The deviation column shows exactly that difference in percent — it grows with every step because the factor 1024 against 1000 compounds.

Sources

IEC 80000-13Binary prefixes KiB, MiB, GiB, TiB against the decimal SI prefixes.BIPM SI BrochureSI base units, prefixes and official SI context.

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