Octal Converter

The Octal Converter translates whole numbers between octal (base 8), decimal (base 10), binary (base 2) and hexadecimal (base 16).

Octal still shows up in Unix file permissions, legacy systems and some embedded and assembly contexts, and bouncing a value between these four bases is the kind of small arithmetic that is easy to get wrong by hand.

Pick the base your number is written in, type or paste it, and all four representations appear at once, each with its own copy button.

Conversions are computed with JavaScript BigInt, so even very large numbers convert exactly without the rounding errors you would hit with floating-point math — useful for cryptographic constants, bit masks and identifiers that exceed the safe integer range.

The tool validates your input against the alphabet of the chosen base, so a stray 9 in an octal value or a g in a hex value is caught immediately with a clear message rather than producing a silently wrong answer.

Common prefixes like 0o, 0b and 0x are accepted and stripped when they match the selected base.

All of this happens locally in your browser; nothing is uploaded, so it is safe for sensitive values and works offline.