GB vs GiB: how to compare storage sizes correctly
A GB contains 1,000,000,000 bytes. A GiB contains 1,073,741,824 bytes. Therefore 1 GB is about 0.9313 GiB, and 1 GiB is about 1.0737 GB. Converting between them changes the number displayed, not the amount of data stored.
Two systems count the same bytes
Decimal units grow in powers of 1,000: a kilobyte is 1,000 bytes, a megabyte is 1,000,000 bytes, and a gigabyte is 1,000,000,000 bytes. Binary units grow in powers of 1,024: a kibibyte is 1,024 bytes, a mebibyte is 1,048,576 bytes, and a gibibyte is 1,073,741,824 bytes.
The symbols make the distinction explicit: kB, MB, and GB are decimal; KiB, MiB, and GiB are binary. Using the full unit avoids an argument about whether an application means 1,000 or 1,024.
Convert through bytes for an exact answer
To convert GB into GiB, multiply by 1,000,000,000 and divide by 1,073,741,824. To convert GiB into GB, reverse those factors. Keep the unrounded result during the calculation, then round for display. This prevents small errors accumulating across a large inventory.
For example, 500 GB equals approximately 465.66 GiB. A 2 GiB archive equals 2,147,483,648 bytes, or approximately 2.1475 GB. Neither conversion loses bytes. The same file simply receives a different numerical label under each counting system.
Explain the apparent missing space
A drive advertised as 1 TB contains one trillion bytes under decimal notation. Expressed in binary units, that is about 931.32 GiB. Seeing a number near 931 therefore does not, by itself, show that hundreds of gigabytes have disappeared.
There are also real capacity deductions. Formatting, operating-system files, recovery areas, and other stored data can reduce usable free space. Unit conversion explains a change of scale; it does not explain every difference between a product label, total formatted capacity, and currently available space. Compare those three quantities separately before troubleshooting a drive.
Check what an application actually means
Some applications use a familiar “GB” label even when the calculation behind it is binary. Others follow decimal notation. If you need an exact comparison, look for a byte count in file properties or the application's documentation rather than inferring the convention from a rounded number.
When sharing a limit with someone else, specify it precisely. “The maximum is 2,000,000,000 bytes” is clearer than “2 gigs.” For a screenshot or report, keep the original unit visible. Silently changing GiB into GB makes a correct number appear inconsistent to the next reader.
Apply the distinction to transfers and budgets
Unit choice affects time estimates too. A decimal 1 GB download at a constant 100 Mbps has an ideal transfer time of 80 seconds. A 1 GiB download at the same rate takes about 85.90 seconds. Those are different file sizes, even though the labels sound similar.
For a backup plan, first total the original byte counts, then convert into the storage provider's unit. For a download estimate, select GB or GiB explicitly. The data converter helps compare both forms; the download-time tool then uses the chosen size consistently. Keep a separate allowance for growth and any overhead that your service actually bills.
Sources & further reading
- NIST: Prefixes for binary multiples
- NIST: SI prefixes and powers of two
- Apple: How storage capacity is measured
These sources support the methods and definitions above. Examples are illustrative; your device, service and settings can change the result.
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