Free Octal Converter
Quick Tips
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Convert numbers between octal (base 8), decimal, binary, and hex.
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Examples
755 (octal)
493 (decimal)
644 (octal)
420 (decimal)
777 (octal)
511 (decimal), 111111111 (binary)
493 (decimal)
755 (octal)
Why Use This Tool?
What problems does this solve?
Setting Unix file permissions requires understanding octal. This tool converts permissions between numeric and other formats, and handles legacy octal values.
Common use cases:
- Understanding and setting Unix file permissions
- Converting legacy octal values in documentation
- Working with chmod commands
- Learning about number system bases
- Debugging code with octal literals
Who benefits from this tool?
System administrators setting permissions. Developers working on Unix/Linux systems. Students learning number systems.
Privacy first: All conversion happens locally in your browser. Your numbers never leave your device.
Frequently Asked Questions
Unix permissions are 9 bits (3 each for owner, group, others). Three bits = one octal digit. So 9 bits become 3 memorable digits like 755 or 644.
7 = rwx (read+write+execute) for owner. 5 = rx (read+execute) for group. 5 = rx for others. This is a typical permission for executable scripts.
In C and some languages, a leading 0 indicates octal. 0755 is octal 755 (decimal 493). This can cause bugs if you accidentally write 010 (octal 8) instead of 10.
Each octal digit equals exactly 3 binary bits. 7 = 111, 5 = 101, 0 = 000. This makes octal-binary conversion trivial - just group binary digits in threes.
Rarely. Some legacy systems, escape sequences (\007 for bell), and certain APIs use octal. Hexadecimal dominates modern computing.
Seven (7). Digits 8 and 9 are not valid in octal. If you see 8 or 9, it is not an octal number.
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