Convert between binary, decimal, hexadecimal and octal number systems — all four bases shown at once.
Also convert text to binary with the Text to Binary tool or encode data with the Base64 Encoder.
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This binary to decimal converter works as a number base converter, hex to decimal calculator, and octal converter for computer science students, developers, and anyone working with different numeral systems. Enter a number in any of the four supported bases and the tool instantly shows the equivalent value in all other bases.
Computers store and process all data as binary — sequences of 0s and 1s — because digital circuits can only represent two states: on and off. A single binary digit is called a bit, and groups of 8 bits form a byte. The decimal number 255, for example, is 11111111 in binary (eight 1-bits, the maximum for one byte), FF in hexadecimal, and 377 in octal. Understanding these conversions is fundamental to computer science, programming, and digital electronics coursework.
Hexadecimal (base 16) uses digits 0–9 and letters A–F to represent values 0 through 15. It is widely used in programming because each hex digit represents exactly four binary bits (a nibble), making it a compact and human-readable way to express binary data. Hex is used in HTML and CSS colour codes, memory addresses, machine code, and network protocol specifications. Octal (base 8) uses digits 0–7, where each octal digit represents exactly three binary bits. It was historically used in early computing and is still found in Unix and Linux file permission notation — the familiar chmod 755 command uses octal values to set read, write, and execute permissions. Understanding these four base systems and being able to convert between them quickly is a core skill for computer science and programming students.