DevToolKit

Chmod Calculator — Instant File Permission Lookup [2026]

Set Unix permissions with checkboxes → get numeric (755) and symbolic (rwxr-xr-x) output instantly. Includes umask mode. Works offline in your browser — no signup needed.

ClassRead (r)Write (w)Execute (x)Value
Owner7
Group5
Other5
Numeric (Octal)
755
Symbolic
rwxr-xr-x
chmod command
chmod 755 filename

What is Chmod Calculator?

Chmod Calculator is a free online tool that helps you calculate Unix/Linux file permissions. The chmod (change mode) command controls who can read, write, or execute a file. Each permission set is represented by a number: read (4), write (2), and execute (1). This calculator lets you visually set permissions and instantly see the numeric and symbolic notation.

How to Use Chmod Calculator

Use the checkboxes to toggle read, write, and execute permissions for the owner, group, and other users. The numeric chmod value (e.g. 755) and symbolic representation (e.g. rwxr-xr-x) update in real time. You can also type a numeric value directly to see the corresponding permissions. Switch to umask mode to calculate the umask value for your desired default permissions.

How Chmod Calculator Works

Each permission (read, write, execute) has a numeric value: read = 4, write = 2, execute = 1. The values are summed for each class (owner, group, other) to produce a three-digit octal number. For example, rwxr-xr-x means owner has read+write+execute (7), group has read+execute (5), and others have read+execute (5), giving 755. The umask is calculated by subtracting the desired permission from 777 (for directories) or 666 (for files).

Common Use Cases

  • Setting correct file permissions on a Linux web server
  • Calculating chmod values for deployment scripts
  • Understanding the difference between chmod 755 and chmod 644
  • Computing umask values for default permission policies
  • Teaching new developers about Unix file permissions

Frequently Asked Questions

What does chmod 755 mean?▼

Chmod 755 means the owner has full permissions (read, write, execute), while group and other users can only read and execute the file. This is commonly used for directories and executable scripts.

What is the difference between chmod 644 and 755?▼

Chmod 644 gives the owner read and write permissions while group and others can only read. Chmod 755 adds execute permission to all three classes. Use 644 for regular files and 755 for directories and scripts.

How does umask work?▼

Umask sets the default permissions for newly created files and directories. It is a mask that is subtracted from the maximum permissions (777 for directories, 666 for files). For example, a umask of 022 results in default permissions of 755 for directories and 644 for files.

Is my data safe when using this tool?▼

Yes. All calculations happen in your browser using JavaScript. No data is sent to any server.

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