Number Base Converter
Convert numbers between decimal, binary, hexadecimal, octal, and ASCII in real time.
About This Tool & Technical Logic
Positional notation expresses a number as digits times powers of a base. Binary (base 2) maps directly to circuit states; hexadecimal (base 16) packs 4 bits per digit, which is why memory addresses, colors, and hashes are written in hex; octal (base 8) survives in Unix file permissions.
This converter parses your input in the chosen base using BigInt, so values beyond 2⁵³ (the floating-point safe range) convert exactly — essential for hash fragments and large IDs. ASCII mode converts each character's code point.
BigInt.parseInt(input, base) → .toString(targetBase); ASCII mode maps each char via codePointAt/now.
How to Use — Step by Step
- 1
Select the input base
The tool validates digits against the base — 9 is rejected in binary, G in decimal — so typos surface immediately.
- 2
Type or paste the value
All other bases update live. Prefixes like 0x and 0b are accepted and ignored.
- 3
Read the ASCII row when relevant
For byte-level work, the ASCII interpretation shows which characters the bytes represent.
Frequently Asked Questions
255 decimal = FF in hexadecimal = 11111111 in binary = 377 in octal. It's the maximum value of one byte.