Programmers read 0xFF, network engineers read 255, and computers underneath it all read 11111111. Four representations, one number.
Updated August 12, 2026, after a fresh review, with updated visuals and links.
Type a value in any base below: binary, decimal, hex and octal equivalents appear together, instantly.
Bases without the headache
Binary (base 2) counts with only 0 and 1 because transistors have two states: 255 in binary is 11111111, eight ones, which is also why bytes top out at 255.
Hexadecimal (base 16) is binary compressed four digits to one character: FF is a byte, which is why memory addresses and color codes (#FF0000 is pure red) speak hex.
Converting by hand means dividing by the target base and keeping remainders in reverse: 255 in hex: 255 over 16 is 15 remainder 15, and 15 is F, hence FF.
Worth remembering
- Memorize the hex alphabet only through F: A=10, B=11, C=12, D=13, E=14, F=15, everything else follows.
- Powers of two (1, 2, 4, 8, 16, 32, 64, 128...) translate instantly to binary: 64 is a 1 followed by six zeros.
Frequently asked
What does 0x mean before a number?
It signals hexadecimal in most programming languages: 0x1F equals 31 in decimal. The tool accepts values with or without the 0x prefix.
Why does octal still exist?
Unix file permissions speak octal (chmod 755): each digit maps exactly to three permission bits, legacy utility that never died.
