The order of magnitude of data may be specified in strictly standards-conformant units of information and multiples of the bit and byte with decimal scaling, or using historically common usages of a few multiplier prefixes in a binary interpretation which has been common in computing until new binary prefixes were defined in the 1990s.

Units of measure The byte has been a commonly used unit of measure for much of the information age to refer to a number of bits. In the early days of computing, it was used for differing numbers of bits based on convention and computer hardware design, but today means 8 bits. A more accurate, but less commonly used name for 8 bits is octet.

Commonly, a decimal SI metric prefix (such as kilo-) is used with bit and byte to express larger sizes (kilobit, kilobyte). But, this is usually inaccurate since these prefixes are decimal, whereas binary hardware size is usually binary. Customarily, each metric prefix, 1000n, is used to mean a close approximation of a binary multiple, 1024n. Often, this distinction is implicit, and therefore, use of metric prefixes can lead to confusion. The IEC binary prefixes (such as kibi-) allow for accurate description of hardware sizes, but are not commonly used.

Entropy This page references two kinds of entropy which are not entirely equivalent. For comparison, the Avogadro constant is entities per mole, based upon the number of atoms in 12 grams of carbon-12 isotope. See Entropy in thermodynamics and information theory. Entropy (information theory), such as the amount of information that can be stored in DNA Entropy (thermodynamics), such as entropy increase of 1 mole of water

List

Binary (bits) Decimal Item Factor Term Factor Term 2−1 10−1 0.415 bits (log2 4/3) – amount of information needed to eliminate one option out of four. 0.6–1.3 bits – approximate information per letter of English text. 20 bit 100 bit 1 bit – 0 or 1, false or true, Low or High (a.k.a. unibit) 1.442695 bits (log2 e) – approximate size of a nat (a unit of information based on natural logarithms) 1.5849625 bits (log2 3) – approximate size of a trit (a base-3 digit) 21 2 bits – a crumb (a.k.a. dibit) enough to uniquely identify one base pair of DNA 3 bits – a triad(e), (a.k.a. tribit) the size of an octal digit 22 nibble 4 bits – (a.k.a. tetrad(e), nibble, quadbit, semioctet, or halfbyte) the size of a hexadecimal digit; decimal digits in binary-coded decimal form 5 bits – the size of code points in the Baudot code, used in telex communication (a.k.a. pentad) 6 bits – the size of code points in Univac Fieldata, in IBM "BCD" format, and in Braille. Enough to uniquely identify one codon of genetic code. The size of code points in Base64; thus, often the entropy per character in a randomly-generated password. 7 bits – the size of code points in the ASCII character set – minimum length to store 2 decimal digits 23 byte (B) 8 bits – (a.k.a. octet or octad(e)) on many computer architectures. – equivalent to 1 "word" on 8-bit computers (Apple II, Atari 8-bit computers, Commodore 64, etc.). – the "word size" for 8-bit console systems including: Atari 2600, Nintendo Entertainment System 101 decabit 10 bits – minimum bit length to store a single byte with error-correcting computer memory – minimum frame length to transmit a single byte with asynchronous serial protocols 12 bits – wordlength of the PDP-8 of Digital Equipment Corporation (built from 1965 to 1990) 24 16 bits – the Basic Multilingual Plane of Unicode, containing character codings for almost all modern languages, and a large number of symbols – the basic unit in UTF-16; the full Universal Character Set (Unicode) can be encoded in one or two of these – commonly used in many programming languages, the size of an integer capable of holding 65,536 different values – equivalent to 1 "word" on 16-bit computers (IBM PC, Commodore Amiga) – the "word size" for 16-bit console systems including: Sega Genesis, Super Nintendo, Mattel Intellivision 25 32 bits (4 bytes) – size of an integer capable of holding 4,294,967,296 different values – size of an IEEE 754 single-precision floating point number – size of addresses in IPv4, the current Internet Protocol – equivalent to 1 "word" on 32-bit processors, including those for the Apple Macintosh, Pentium-based PC, PlayStation, GameCube, Xbox, Wii 36 bits – size of word on Univac 1100-series computers and Digital Equipment Corporation's PDP-10 56 bits (7 bytes) – cipher strength of the DES encryption standard 26 64 bits (8 bytes) – size of an integer capable of holding 18,446,744,073,709,551,616 different values – size of an IEEE 754 double-precision floating point number – equivalent to 1 "word" on 64-bit computers (Power, PA-RISC, Alpha, Itanium, SPARC, x86-64 PCs and Macintoshes). – the "word size" for 64-bit console systems including: Nintendo 64, PlayStation 2, PlayStation 3, Xbox 360 80 bits (10 bytes) – size of an extended precision floating point number, for intermediate calculations that can be performed in floating point units of most processors of the x86 family. 102 hectobit 100 bits 27 128 bits (16 bytes) – size of addresses in IPv6, the successor protocol of IPv4 – minimum cipher strength of the Rijndael and AES encryption standards, and of the widely used MD5 cryptographic message digest algorithm – size of an SSE vector register, included as part of the x86-64 standard 160 bits (20 bytes) – maximum key length of the SHA-1, standard Tiger (hash function), and Tiger2 cryptographic message digest algorithms 28 256 bits (32 bytes) – minimum key length for the recommended strong cryptographic message digests – size of an AVX2 vector register, present on newer x86-64 CPUs 29 512 bits (64 bytes) – maximum key length for the standard strong cryptographic message digests in 2004 – size of an AVX-512 vector register, present on some x86-64 CPUs 103 kilobit(kbit) 1,000 bits (125 bytes) 210 kibibit(Kibit) 1,024 bits (128 bytes) - RAM capacity of the Atari 2600 1,288 bits (161 bytes) – approximate maximum capacity of a standard magnetic stripe card 211 2,048 bits (256 bytes) – RAM capacity of the stock Altair 8800 212 4,096 bits (512 bytes) – typical sector size, and minimum space allocation unit on computer storage volumes, with most file systems