What is a Bit?

The bit is the smallest unit of digital information, representing a single binary choice between two states (typically 0 or 1, true or false, on or off). Coined by mathematician John Tukey in 1947 (from 'binary digit'), and formalized by Claude Shannon in his 1948 information theory papers, the bit is the foundation of all modern computing, telecommunications, and information storage. Bit-rates measure data transmission speeds (megabits per second, Mbps, for internet connections), and information-theory entropy is calculated in bits. A single yes/no question carries 1 bit of information; an 8-bit byte represents 256 possible values. The bit relates to the byte (8 bits = 1 byte), the kilobit (1,000 bits = 1 kbit, used in telecom), and the kibibit (1,024 bits = 1 Kibit, used in computing). Modern fiber-optic networks transmit terabits per second.

Visual reference for how the bit relates to other data units. Each row links to the full converter for that pair.

• Network throughput (bps, Mbps, Gbps)
• Cryptography key lengths (e.g., 256-bit AES)
• Compression algorithms and file header specs

• ✓8 bits = 1 byte.
• ✓Mbps ≠ MB/s — divide by 8 to get bytes per second.
• ✓Encryption strength often given in bits (128, 256).

• ✗Mixing b (bit) and B (byte) — 8× difference.
• ✗Thinking a 1 Gbps link delivers 1 GB/s — it's 125 MB/s.
• ✗Reading "256-bit encryption" as "256-byte" — totally different strength.