What does chmod 755 mean?

chmod 755 gives the owner full permissions (read, write, execute) and everyone else read and execute only. In symbolic notation it is rwxr-xr-x. It is the standard setting for directories, scripts, and binaries that others need to run but not modify.

What is the difference between chmod 755 and 644?

755 includes the execute bit, 644 does not. Use 755 for directories and executables (execute on a directory means it can be entered), and 644 for regular files like HTML, images, and configs, which only need to be read.

Almost never. chmod 777 lets any user on the system read, modify, and execute the file, which is a common attack vector on shared hosting. If a web server needs write access, give ownership to the right user with chown and use 755 or 775 instead.

What permissions should SSH keys have?

Private keys must be 600 (rw-------) and the ~/.ssh directory 700 (rwx------). If they are more open, SSH refuses to use them with the error "Permissions are too open". The public key (.pub) and authorized_keys can be 644.

How do I apply chmod recursively?

Use chmod -R to recurse into directories, but avoid one blanket value for everything. The safe pattern is: find . -type d -exec chmod 755 {} + for directories and find . -type f -exec chmod 644 {} + for files, so files do not become executable.

Free Chmod Calculator: Unix File Permissions Made Easy

What is a Chmod Calculator?

A chmod calculator helps you convert between the different ways Unix and Linux represent file permissions. The chmod command uses either numeric (octal) values like 755 or symbolic notation like rwxr-xr-x to set who can read, write, or execute a file. This tool lets you toggle permissions visually and instantly see the numeric value, symbolic string, and the full chmod command.

Key Features

Interactive Checkboxes: Toggle read, write and execute for owner, group and others.
Numeric Input: Type an octal value (e.g. 755) and see the corresponding permissions.
Symbolic Notation: View the permission string as shown by ls -l.
Special Permissions: Support for setuid, setgid and sticky bit (4-digit octal).
Common Presets: One-click presets for 755, 644, 777, 600 and more.
Copy to Clipboard: Copy the chmod command, octal value, or symbolic string.

How to use the Chmod Calculator

Toggle the read, write and execute checkboxes for each role (owner, group, others).
Or type a numeric permission value directly (e.g. 755 or 0755).
Review the result: octal, symbolic and the full chmod command.
Copy the command and run it in your terminal.

How octal permissions are calculated

Each permission has a numeric weight: read = 4, write = 2, execute = 1. Add them up per role to get one digit each for owner, group, and others. For example, rwxr-xr-- is (4+2+1)(4+0+1)(4+0+0) = 754. A leading fourth digit encodes special bits: setuid = 4, setgid = 2, sticky = 1, so chmod 4755 is 755 plus setuid.

Common Permission Values

755 (rwxr-xr-x): Standard for executables and directories. Owner can do everything, others can read and execute.
644 (rw-r--r--): Standard for files. Owner can read and write, others can only read.
700 (rwx------): Private directory, typical for ~/.ssh. No access for group or others.
600 (rw-------): Private file, required for SSH private keys and common for credential files like .env.
664 (rw-rw-r--): Group-writable file, used in shared project directories.
750 (rwxr-x---): Executable or directory shared with the group but hidden from others.
440 (r--r-----): Read-only for owner and group, the setting sudoers expects.
1777 (rwxrwxrwt): World-writable with the sticky bit, like /tmp: anyone can create files, only owners can delete their own.
777 (rwxrwxrwx): Full access for everyone. Almost always the wrong answer, fix ownership with chown instead.

Typical permission fixes

"Permissions are too open" from SSH: run chmod 600 ~/.ssh/id_rsa and chmod 700 ~/.ssh.
Web server files: directories 755, files 644, config files with secrets 640 with the web server group as owner.
Shell script will not run: add the execute bit with chmod +x script.sh (symbolic mode works without touching other bits).
Recursive fix without making files executable: find . -type d -exec chmod 755 {} + then find . -type f -exec chmod 644 {} +.

Working on a server anyway? The Cron Generator builds scheduled job expressions visually, and the htpasswd Generator creates Apache and Nginx basic auth credentials.

Role	Read (4)	Write (2)	Execute (1)	Octal
Owner (u)				7
Group (g)				5
Others (o)				5

Chmod Calculator