About this tool
Octal (base-8) uses the digits 0–7, where each position is a power of eight. It shows up most often in Unix file permissions (755) and some legacy systems. Converting to decimal expands each digit by its place value — octal 17 is 1×8 + 7 = 15.
Paste an octal value and the decimal equivalent appears immediately. The tool validates that only digits 0–7 are present and ignores spaces, so a stray 8 or 9 is flagged rather than silently mis-converted.
Conversion happens locally — nothing you enter is uploaded.
Frequently asked questions
Where is octal still used?
Most commonly in Unix file permissions, where 755 or 644 encode read/write/execute bits. It also appears in some older file formats and hardware contexts.
What if I enter an 8 or 9?
Those aren't valid octal digits, so the tool flags the input as invalid instead of guessing. Octal only uses 0 through 7.
How do I convert file permissions?
For chmod-style permissions, the chmod calculator maps octal values to read/write/execute bits and the symbolic rwx notation directly.