chmod Permissions Calculator

In Linux and Unix-like operating systems, file permissions determine who can read, write, or execute files. The chmod (change mode) command alters these permissions using either octal numbers (e.g. 755) or symbolic strings (e.g. u+rwx).

Use this interactive calculator to toggle permission checkboxes, view the symbolic string representation, and calculate the octal code to use in your terminal.

Interactive Calculator

[ CHMOD CALCULATOR ]

Class

Read (4)

Write (2)

Execute (1)

User (Owner)

Group

Others

Symbolic String: -rwxr-xr-x

Octal Notation: 755

Terminal Command:

chmod 755 filename

    <!-- Explanation box -->
    <div style="margin-top: 15px; font-size: 0.9em; line-height: 1.5; opacity: 0.9;">
        <span class="tui-key">[INFO]</span> <span id="permission-explanation">Calculating privileges...</span>
    </div>

    <!-- Access Rights Breakdown Table (Upgrade) -->
    <div class="tui-box" style="margin-top: 25px; margin-bottom: 0;">
        <div class="tui-box-title">[ ACCESS CAPABILITY MATRIX ]</div>
        <table style="width: 100%; border-collapse: collapse; margin-top: 5px; font-size: 0.85em;">
            <thead>
                <tr>
                    <th style="text-align: left; padding: 6px;">Action</th>
                    <th style="text-align: center; padding: 6px;">Owner</th>
                    <th style="text-align: center; padding: 6px;">Group</th>
                    <th style="text-align: center; padding: 6px;">Others</th>
                </tr>
            </thead>
            <tbody>
                <tr>
                    <td style="padding: 6px;">Read File / List Dir (<code>r</code>)</td>
                    <td id="cap-ur" style="text-align: center; padding: 6px; font-weight: bold;">Yes</td>
                    <td id="cap-gr" style="text-align: center; padding: 6px; font-weight: bold;">Yes</td>
                    <td id="cap-or" style="text-align: center; padding: 6px; font-weight: bold;">Yes</td>
                </tr>
                <tr>
                    <td style="padding: 6px;">Modify File / Write Dir (<code>w</code>)</td>
                    <td id="cap-uw" style="text-align: center; padding: 6px; font-weight: bold;">Yes</td>
                    <td id="cap-gw" style="text-align: center; padding: 6px; font-weight: bold;">No</td>
                    <td id="cap-ow" style="text-align: center; padding: 6px; font-weight: bold;">No</td>
                </tr>
                <tr>
                    <td style="padding: 6px;">Execute File / Enter Dir (<code>x</code>)</td>
                    <td id="cap-ux" style="text-align: center; padding: 6px; font-weight: bold;">Yes</td>
                    <td id="cap-gx" style="text-align: center; padding: 6px; font-weight: bold;">Yes</td>
                    <td id="cap-ox" style="text-align: center; padding: 6px; font-weight: bold;">Yes</td>
                </tr>
            </tbody>
        </table>
    </div>
</div>

What Do the Numbers Mean?

In Linux, file permissions are managed using three octal digits representing three access classes:

First Digit: Owner permissions.
Second Digit: Group permissions.
Third Digit: Others permissions.

To calculate each digit, you add up the values of the permissions granted:

Read (r): 4
Write (w): 2
Execute (x): 1
No Permission (-): 0

For example:

Read + Write + Execute = 4 + 2 + 1 = 7
Read + Execute = 4 + 0 + 1 = 5
Read only = 4 + 0 + 0 = 4

Therefore, 755 grants the owner full control (7), and lets group members and everyone else read and execute files (5) but not modify them.

Common Configurations Quick Reference

755 - Standard executable file: Owner can modify/execute; everyone else can read/execute. Useful for scripts.
644 - Standard text file: Owner can modify; everyone else can only read. Safe default for configs, HTML, and assets.
700 - Private script/keys: Only the owner can access or run. Excellent for SSH key folders (~/.ssh) or private logs.
600 - Private configuration: Only the owner can read or write (e.g. private SSH keys like id_rsa).