Calculate Linux/Unix file permissions in octal and symbolic notation
Free chmod calculator to convert between octal (755, 644) and symbolic (rwxr-xr-x) Linux file permissions. Generate a ready-to-copy chmod command instantly. 100% client-side.
| Octal | Symbolic | Permissions | Common Use |
|---|---|---|---|
755 | rwxr-xr-x | Owner: all, Group/Others: read+exec | Executable scripts, web directories |
644 | rw-r--r-- | Owner: read+write, Group/Others: read | HTML, CSS, images, config files |
777 | rwxrwxrwx | Everyone: all permissions | Temporary/dev only (security risk) |
700 | rwx------ | Owner: all, no access for others | Private scripts, home directories |
600 | rw------- | Owner: read+write only | SSH keys, private configs |
444 | r--r--r-- | Everyone: read only | Read-only files, public docs |
750 | rwxr-x--- | Owner: all, Group: read+exec | Group-accessible programs |
664 | rw-rw-r-- | Owner+Group: read+write, Others: read | Shared project files |
640 | rw-r----- | Owner: read+write, Group: read | Log files, sensitive configs |
400 | r-------- | Owner: read only | SSH private keys (strict) |
Click any row to load those permissions
chmod (change mode) is a Unix/Linux command that sets file and directory permissions. Every file has three permission categories: Owner (the user who created it), Group (users in the file's group), and Others (everyone else). Each category can have Read, Write, and Execute permissions.
Each permission has a numeric weight: Read = 4, Write = 2, Execute = 1. Add them together for each role:
The three digits in chmod 755 represent Owner (7), Group (5), Others (5).
Symbolic notation uses letters: r (read), w (write), x (execute), - (no permission). The 9-character string is grouped in threes: rwxr-xr-x = Owner(rwx) + Group(r-x) + Others(r-x).
You can also use symbolic mode with chmod: chmod u=rwx,g=rx,o=rx filename is equivalent to chmod 755 filename. Use + to add and - to remove permissions: chmod g+w filename adds write permission for the group.
Use chmod -R to change permissions recursively on a directory and all its contents: chmod -R 755 /var/www/html. This applies the same permission to every file and subdirectory inside.
However, files and directories usually need different permissions. A better approach is to set them separately:
find /path -type d -exec chmod 755 {} +find /path -type f -exec chmod 644 {} +This ensures directories are traversable (need execute) while files remain non-executable.
chmod +x filename adds execute permission for all users. This is the fastest way to make a script runnable. For finer control:
After adding execute permission, run a script with ./script.sh. If you see "Permission denied", you likely need to run chmod +x script.sh first.
Linux uses umask to determine default permissions for new files and directories. The default umask is typically 022, which means:
644 (rw-r--r--)755 (rwxr-xr-x)Check your current umask with the umask command. A more restrictive umask like 077 creates files as 600 and directories as 700, giving access only to the owner.
chmod (change mode) is a Unix/Linux command that changes file and directory permissions. It controls who can read, write, or execute a file. Permissions are set for three categories: Owner, Group, and Others.
chmod 755 sets rwxr-xr-x. The owner gets full permissions (7 = read+write+execute). Group and others get read and execute (5 = read+execute). This is the standard permission for executable scripts and web directories.
chmod 644 sets rw-r--r--. The owner can read and write (6). Group and others can only read (4). This is the default for regular files like HTML pages, images, and configuration files.
chmod 777 gives everyone full read, write, and execute permissions. Any user on the system can modify or delete the file. Never use 777 in production. Use 755 for directories and 644 for files instead.
SSH private keys must be chmod 600 (rw-------) or chmod 400 (r--------). SSH will refuse to use a key file with permissions that are too open. The .ssh directory should be chmod 700.
Octal uses numbers: chmod 755 file. Symbolic uses letters: chmod u=rwx,g=rx,o=rx file. Both produce the same result. Octal sets all permissions at once; symbolic can make relative changes like chmod g+w file.
Web files should be 644 (rw-r--r--) and web directories should be 755 (rwxr-xr-x). The web server needs read access to serve files and execute access to traverse directories. Only the owner should have write access.
Run chmod +x filename to add execute permission for all users, or chmod u+x filename for the owner only. For scripts, chmod 755 is the most common choice, giving the owner full control and others read+execute access.
Use chmod -R 755 /path/to/directory to change permissions recursively on a directory and all its contents. For best practice, set directories and files separately: find /path -type d -exec chmod 755 {} + for directories and find /path -type f -exec chmod 644 {} + for files.
chmod +x adds execute permission for all users (owner, group, others). It's the quickest way to make a shell script or binary executable. Use chmod u+x to add execute only for the owner. If you see "Permission denied" when running a script, you need chmod +x.
New files default to 644 (rw-r--r--) and new directories to 755 (rwxr-xr-x). This is controlled by umask, typically set to 022. The umask subtracts from the maximum: 666 - 022 = 644 for files, 777 - 022 = 755 for directories.
chmod 400 sets r--------. Only the file owner can read it. No one can write or execute. This is the strictest common permission, used for SSH private keys and sensitive credentials. It's more restrictive than chmod 600, which also allows the owner to write.