Octal Converter
Convert octal numbers (base 8) to and from decimal, binary, and hexadecimal formats. Octal uses digits 0-7 and is commonly used in Unix/Linux file permissions. Each octal digit represents exactly 3 binary bits, making it useful for certain computing applications.
Decimal
Octal
Common Conversions
0
0o0
7
0o7
8
0o10
64
0o100
100
0o144
255
0o377
511
0o777
512
0o1000
Unix File Permissions
644
rw-r--r-- (files)
755
rwxr-xr-x (dirs)
600
rw------- (private)
777
rwxrwxrwx (all)
700
rwx------ (scripts)
666
rw-rw-rw- (shared)
FAQ
What is octal?
Octal is a base-8 number system using digits 0-7. Each octal digit represents exactly 3 binary bits, which made it historically useful in computing before hexadecimal became more common.
Where is octal used today?
Octal is primarily used in Unix/Linux file permissions (e.g., chmod 755). Each permission set (read, write, execute) for owner, group, and others maps to 3 bits, perfectly represented by one octal digit.
How do Unix file permissions work with octal?
In Unix, read=4, write=2, execute=1. Sum these for each category. For example, 755 means owner has all permissions (7=4+2+1), while group and others have read+execute (5=4+1).