Chmod Calculator
Calculate Unix file permissions with interactive checkboxes. Convert between numeric (755) and symbolic (rwxr-xr-x) notation. Reverse input, common presets. Free chmod calculator.
Why Use a Chmod Calculator?
Unix file permissions use a combination of numeric and symbolic notation that can be confusing. A chmod calculator lets you visually set read, write, and execute permissions for owner, group, and others, instantly seeing the numeric mode, symbolic notation, and the full chmod command. Our tool also supports reverse input and common presets.
Key Features
- Interactive permission checkboxes for owner, group, and others
- Displays numeric (755), symbolic (rwxr-xr-x), and full notation
- Reverse: input numeric mode to see permissions
- 8 common presets: 644, 755, 777, 700, 600, 750, 666, 400
- File type indicator (d for directory, - for file)
How It Works
- Set file type (file or directory)
- Toggle read/write/execute for owner, group, and others
- Or enter a numeric mode (e.g., 755) to set permissions in reverse
- Copy the chmod command for your terminal
Technical Details
This calculator follows the standard Unix permission model with three categories (owner, group, others) and three permission types (read, write, execute). The numeric notation uses octal (base-8) digits where each bit represents a permission: 4=read, 2=write, 1=execute. The tool is 100% client-side with no external dependencies.
Frequently Asked Questions
What does chmod 755 mean?
chmod 755 means the owner has read (4), write (2), and execute (1) permissions (7=4+2+1), the group has read and execute (5=4+1), and others have read and execute (5=4+1). This is the default for directories and executable scripts.
What is the difference between numeric and symbolic notation?
Numeric notation uses octal numbers (e.g., 755) where each digit represents the sum of read (4), write (2), and execute (1) for owner, group, and others. Symbolic notation uses letters like rwxr-xr-x to show permissions directly.
When should I use chmod 777?
chmod 777 gives full read, write, and execute permissions to everyone. It should be used with extreme caution as it's a security risk. Only use it in development environments or when absolutely necessary.
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