What is Chmod?
chmod (change mode) is a Unix/Linux command that sets file and directory permissions. Permissions are represented as three octal digits (e.g., 755) controlling read (4), write (2), and execute (1) access for the owner, group, and others. This calculator provides an interactive grid to set permissions and shows the equivalent chmod command, symbolic notation, and umask value.
Common use cases
- Calculating file permissions for deployment scripts
- Understanding what chmod 755 or chmod 644 means
- Converting between numeric and symbolic permission notation
- Setting correct permissions for web server files
- Calculating umask values for default permissions
How to use
- 1Tick read, write and execute for owner, group and others — or type an octal mode like 755.
- 2Read the symbolic form, explanation and ls -la preview, or start from a common preset.
- 3Set the file name and copy the chmod command (⌘↵); use the umask and converter sections as needed.
Frequently asked questions
What does chmod 755 mean?
chmod 755 means: owner can read, write, and execute (7 = 4+2+1); group can read and execute (5 = 4+1); others can read and execute (5 = 4+1). This is the standard permission for executable files and directories.
What is the difference between 644 and 755?
644 (rw-r--r--) is for regular files: owner can read/write, everyone else can only read. 755 (rwxr-xr-x) adds execute permission, required for scripts, programs, and directories (directories need execute to be entered).