Bought a 64 GB flash drive but your computer only shows 59.6 GB available? It's not a defect — it's a mathematical difference between two measurement standards.
Storage device manufacturers (HDDs, SSDs, flash drives, memory cards) follow the decimal standard of the International System of Units, in which 1 gigabyte (GB) equals exactly 1,000,000,000 bytes (10 to the 9th power). This is the same standard used for any other metric unit: 1 kilo is 1,000, 1 mega is 1,000,000, and so on.
Operating systems like Windows, however, have historically calculated storage space using powers of 2, since computers operate internally in binary. Under this standard, 1 "gigabyte" that the system displays actually equals 1,073,741,824 bytes (2 to the 30th power) — a value about 7.4% larger than the decimal gigabyte used by the manufacturer. This binary value is technically called a gibibyte (GiB), but most operating systems incorrectly label it as "GB" in their interface, causing confusion.
This is why a flash drive sold as "64 GB" (64,000,000,000 bytes, in the manufacturer's standard) shows up in Windows as approximately 59.6 GB available — there was no actual loss of space or product defect, it is simply the same number of bytes being displayed under two different measurement rulers. The larger the device capacity, the bigger this apparent percentage difference gets.
macOS, since 2009, and most Linux distributions have already adopted the decimal standard for operating system display as well, calculating "GB" the same way manufacturers do — which is why the same 64 GB flash drive tends to show a capacity closer to the advertised value on those systems, compared to Windows.
The difference between the decimal and binary standards grows with the device capacity. For an 8 GB flash drive, the difference is about 0.5 GB; for a 1 TB (terabyte) disk, the difference reaches almost 100 GB between the manufacturer's decimal value (1,000,000,000,000 bytes) and the binary value displayed by Windows (about 931 GB). For this reason, the feeling of "missing space" is more noticeable on larger capacity devices — the larger the disk, the greater the absolute difference, although the percentage (~7.4%) is always the same.
This divergence has already generated lawsuits in several countries, with consumers alleging false advertising by storage manufacturers. Courts have mostly ruled in favor of manufacturers, recognizing that the decimal standard is legitimate and aligned with the universal metric use of prefixes (kilo = 1,000, mega = 1,000,000). The responsibility for the confusion falls more on operating systems that label gibibytes as "GB" than on manufacturers who follow the correct decimal standard.
To avoid confusion, the IEC recommendation is to always use binary prefixes (KiB, MiB, GiB, TiB) when referring to powers of 2, and decimal prefixes (KB, MB, GB, TB) when referring to powers of 10. The TudoConversor data storage converter follows this convention, offering both families of units and allowing clear conversion between the decimal and binary standards, eliminating the ambiguity that generates most doubts about storage capacity.
A related confusion affects download speed expectations. When an internet plan advertises "100 Mbps", that is megabits per second, and the actual download speed in megabytes per second is about 12.5 MB/s, since 1 byte = 8 bits. A 1 GB file downloaded at 100 Mbps takes about 80 seconds, not 10 seconds as someone might assume by confusing megabits with megabytes. Understanding this distinction helps set realistic expectations for internet performance and avoids the common frustration of feeling that a contracted speed is not being delivered, when in fact the measurement unit was simply misunderstood.
The standardization of binary prefixes by the IEC in 1998 (KiB, MiB, GiB, TiB) resolved an ambiguity that had persisted since the early days of computing, when engineers used "kilobyte" to mean both 1,000 bytes and 1,024 bytes depending on context. The formal definition establishes that 1 kibibyte (KiB) = 1,024 bytes, while 1 kilobyte (KB) = 1,000 bytes. Despite the standardization, software and operating systems were slow to adopt the new nomenclature, and the confusion persists in everyday vocabulary, where most people still use "KB" and "MB" to refer to binary values.
In RAM, the convention is almost always binary: a computer with "16 GB of RAM" actually has 16 gibibytes (17,179,869,184 bytes), because memory circuits are addressed in powers of 2. In disk storage, however, manufacturers use the decimal standard. This difference in convention between memory and storage — binary in RAM, decimal on disk — is an additional source of confusion, since the same number "16 GB" represents slightly different byte counts depending on whether it refers to memory or disk.