The Unix permissions calculator converts between numeric (755, 644) and symbolic (rwxr-xr-x) chmod formats instantly. Click the checkboxes to build permissions visually, or enter the numeric or symbolic value directly.
Visual Permission Builder
Converted Values
Common Presets
How to Use the Unix Permissions Calculator
Unix file permissions control who can read, write, and execute files. The chmod command accepts either numeric (octal) or symbolic notation.
Step 1: Build Permissions Visually
Click the r/w/x buttons to toggle permissions for owner, group, and other. The numeric and symbolic values update in real time. This visual approach makes it easy to understand what 755 means before memorizing it.
Step 2: Use Presets for Common Cases
Click any preset to load the configuration. The most common permissions: 755 for executables and directories (owner can write, everyone can read/execute), 644 for web files (owner can write, others read-only), 600 for private configuration files with passwords.
Step 3: Apply with chmod
Run chmod 755 script.sh or chmod u+x script.sh. For recursive directory permission changes: chmod -R 755 /var/www/html. Use ls -la to verify the applied permissions.
Frequently Asked Questions
Is this chmod permissions calculator free?
Yes, completely free. All conversions run in your browser with no account required.
What do the three digits in chmod mean?
The three digits represent owner, group, and other permissions respectively. Each digit is the sum of: 4 (read), 2 (write), 1 (execute). So 7 = 4+2+1 = rwx (full permissions), 6 = 4+2 = rw- (read/write), 5 = 4+1 = r-x (read/execute), 4 = r-- (read only), 0 = --- (no permissions).
What does chmod 755 mean?
chmod 755 means: owner has rwx (7 = read+write+execute), group has r-x (5 = read+execute), others have r-x (5 = read+execute). This is the standard permission for executable files and directories that should be readable/executable by all but only writable by the owner.
What does chmod 644 mean?
chmod 644 means: owner has rw- (6 = read+write), group has r-- (4 = read only), others have r-- (4 = read only). This is the standard permission for regular files that should be readable by everyone but only writable by the owner.
What is the sticky bit and setuid?
The sticky bit (chmod 1xxx) on a directory prevents users from deleting files they don't own — used on /tmp. Setuid (chmod 4xxx) on an executable makes it run as the file owner rather than the calling user — used on /usr/bin/passwd. Setgid (chmod 2xxx) on a directory makes new files inherit the directory's group.
What permissions should I set on web server files?
Recommended web server permissions: directories 755 (drwxr-xr-x), PHP/HTML files 644 (-rw-r--r--), config files with secrets 600 (-rw-------), executable scripts 755. Never use 777 (world-writable) — it creates a significant security vulnerability.