Chmod Calculator

The chmod command changes file and directory permissions on Linux, macOS, and other Unix-like systems. Permissions are assigned independently to three classes: the file owner, members of the file's group, and all other users. Each class can receive read, write, and execute access. This calculator turns those choices into both the familiar three-digit octal mode and the nine-character symbolic display. Numeric chmod notation assigns a value to each permission. Read is worth four, write is worth two, and execute is worth one. Adding the selected values produces one digit from zero through seven for each class. A digit of seven means read, write, and execute are all enabled; six means read and write; five means read and execute; and zero grants no permissions. The digits are ordered owner, group, then others, so 755 gives full access to the owner and read plus execute access to everyone else. Symbolic output expresses the same settings with letters and hyphens. Each three-character group always follows the order read, write, execute. A hyphen marks a permission that is not granted. For example, rwxr-xr-x corresponds to 755, while rw------- corresponds to 600. The displayed command uses absolute numeric mode, replacing all nine ordinary permission bits at once. Choose permissions according to what the file or directory needs, not simply to make an error disappear. Regular private files commonly use 600, shared readable files often use 644, private directories may use 700, and public web directories commonly use 755. Execute means something different for directories: it permits traversal and access to entries, while read permits listing names. Removing directory execute access can therefore block access even when read remains enabled. Avoid mode 777 unless every local user truly requires write access. Broad write permission can allow unwanted modification or replacement. This basic calculator covers owner, group, and others bits but does not include setuid, setgid, sticky bits, access control lists, or recursive behavior. Review ownership and application requirements before running chmod on production systems, and be especially cautious with recursive commands.