Chmod Permission Calculator
| Type | Read (r) | Write (w) | Execute (x) | Octal |
|---|---|---|---|---|
| Owner (User) | 5 | |||
| Group | 5 | |||
| Others (World) | 5 |
chmod 755 filename
Why Use a Chmod Calculator?
Linux file permissions are expressed in two formats — symbolic (rwxr-xr-x) and octal (755). Calculating the correct permission value manually is error-prone, especially with less common permission sets. Our calculator lets you click checkboxes to set permissions visually, and instantly generates both the octal value and the ready-to-use chmod command.
Visual Permission Builder
Click checkboxes for owner/group/others read/write/execute — see values update instantly
Bidirectional Sync
Type an octal value (like 755) and checkboxes update automatically, or vice versa
Ready Command Output
Generates the complete chmod command ready to paste directly into your terminal
How to Calculate Permissions
Check Desired Permissions
Click the read/write/execute checkboxes for Owner, Group, and Others
See Octal & Symbolic
The octal value (e.g., 755) and symbolic notation (rwxr-xr-x) update instantly
Copy the Command
Copy the generated chmod command and run it in your terminal
Common Chmod Scenarios
Web Server Files
Set 644 for HTML/CSS/JS files (owner read/write, group/others read-only) on Apache or Nginx
Executable Scripts
Set 755 for shell scripts (owner full, group/others read+execute) to make them runnable
SSH Key Files
SSH requires private keys to be 600 (owner read/write only) or SSH will refuse to use them
Upload Directories
Set 775 for web upload directories so the web server process can write user-uploaded files
Linux Permission Best Practices
✓ Never Use 777 in Production
chmod 777 gives everyone full read/write/execute access — a serious security risk. Use the minimum permissions necessary.
✓ Principle of Least Privilege
Always grant the minimum permissions needed. Start restrictive (600) and add permissions as needed rather than starting open.
✓ Be Careful with -R Recursion
chmod -R applies permissions recursively to all files and directories. Setting execute on directories is usually correct, but not always for files.
✓ Understand umask
The umask value subtracts permissions from the default. A umask of 022 means new files get 644 and new directories get 755 by default.
❓ Frequently Asked Questions
What does chmod 755 mean?
755 means: Owner (7) = read+write+execute, Group (5) = read+execute, Others (5) = read+execute. It's the standard permission for executable files and public directories.
What is the difference between 644 and 755?
644 (rw-r--r--): Owner can read/write, others can only read — used for regular files. 755 (rwxr-xr-x): Owner can also execute — used for scripts and directories.
Why does my SSH key need 600 permissions?
SSH refuses to use private keys that are accessible by any other user. The 600 permission (rw-------) ensures only the owner can read/write the key, preventing unauthorized access.
What does the execute bit on a directory mean?
For directories, the execute bit means 'traverse' — it allows users to enter the directory and access files within it. Without execute permission on a directory, users cannot cd into it even if they have read permission.