Chmod Calculator
Convert between numeric (755) and symbolic (rwxr-xr-x) Linux file permissions. Shows owner, group, and other breakdowns with chmod commands. Essential for Linux/Unix system administration.
Parameters
Enter 3-digit numeric permission or 9-char symbolic (rwxr-xr-x).
Results
Octal numeric representation used with chmod
Other results (7)
rwxr-xr-x
Human-readable symbolic representation
Owner can read, Owner can write, Owner can execute
Group can read, Group can execute
Others can read, Others can execute
chmod 755 <file>
The shell command to set these permissions
Standard permission for executable files and directories. Owner has full control, others can read and execute.
Bit | Value | Permission ----|-------|---------- r | 4 | Read w | 2 | Write x | 1 | Execute - | 0 | None
How Unix permission bits map to numeric values
Why Choose Chmod Calculator
The Chmod Calculator converts Unix file permissions between numeric (755) and symbolic (rwxr-xr-x) notation. It breaks down owner, group, and other permissions, generates chmod commands, and provides a security assessment of the permission set.
- ✓Converts between numeric (octal) and symbolic permission formats
- ✓Breaks down permissions for owner, group, and others
- ✓Generates ready-to-use chmod shell commands
- ✓Provides security assessment highlighting risky permissions
How to Use
- 1Enter a numeric permission code (like 755) or symbolic string (like rwxr-xr-x)
- 2View the converted representation in both formats
- 3Read the breakdown of what each role (owner, group, other) can do
- 4Copy the chmod command to apply these permissions
- 5Review the security assessment to understand risk level
Frequently Asked Questions (FAQ)
What does chmod 755 mean?
chmod 755 sets permissions so the owner can read, write, and execute (7), while the group and others can read and execute (5). This is the standard permission for executable files and directories.
How do Unix permission numbers work?
Unix permissions use three bits per role (read=4, write=2, execute=1). Add the bits together: rwx = 4+2+1 = 7, r-x = 4+1 = 5, r-- = 4. Three roles (owner, group, other) give a 3-digit octal number like 755.
Why is 777 dangerous?
Permission 777 gives full read, write, and execute access to everyone on the system. Any user can modify or delete the file. This should only be used in very specific, controlled scenarios and never for sensitive files or web directories.
What permissions should I use for web server files?
For most web files, use 644 (owner read/write, others read) for files and 755 (owner full, others read/execute) for directories. Configuration files with sensitive data should be 600 (owner read/write only).
What is the difference between files and directories for permissions?
For files, execute means the file can be run as a program. For directories, execute means you can enter (cd into) the directory and access its contents. You need execute permission on a directory to access files inside it, even if you have read permission on the files.
Authoritative References & Sources
chmod - Linux man page
View SourceFile System Permissions - Wikipedia
View SourceUnix Permissions Calculator
View SourceRelated Tools
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