Octal Converter

About the Octal Converter

Octal is the base-8 number system, using digits 0 through 7. It was popular on early computers because one octal digit maps directly to three binary digits, making it a compact shorthand for binary values. Today octal remains in common use for Unix and Linux file permission codes — for instance, chmod 755 uses octal values to set read, write, and execute permissions.

Enter any octal number and the tool instantly converts it to binary, decimal, hexadecimal, and ASCII (where applicable).

Octal and Unix Permissions

Unix file permissions are typically expressed as three octal digits. Each digit is the sum of read (4), write (2), and execute (1) values for owner, group, and others respectively. For example, 755 means the owner has full permissions (7 = 4+2+1) while group and others have read and execute only (5 = 4+1).

Common Uses

• Decoding and setting Unix/Linux file permission codes
• Converting between octal and binary in embedded systems where 3-bit groupings are significant
• Reading legacy escape sequences in C strings (e.g. \033 for ESC)
• Working with older communication protocols that use octal addressing