Chmod Calculator

Convert between symbolic and numeric Unix file permissions with a visual chmod calculator.

Chmod Calculator tool

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Example

Input: Numeric 644

Result: Symbolic rw-r--r--, ls -l Output -rw-r--r--, chmod Command: chmod 644 filename

Each octal digit is read (4) + write (2) + execute (1) for owner, group and others: 6 is rw- and 4 is r--.

Common chmod Permissions

NumberLettersMeaning
777rwxrwxrwxFull access for everyone
755rwxr-xr-xOwner full, others read and execute
750rwxr-x---Owner full, group read and execute
700rwx------Owner full, no access for others
644rw-r--r--Owner read and write, others read only
600rw-------Owner read and write, no access for others
444r--r--r--Read only for everyone
400r--------Read only for owner
1777rwxrwxrwtShared folder with sticky bit, like /tmp
4755rwsr-xr-xSetuid program, runs as its owner
2775rwxrwsr-xSetgid folder, new files inherit its group

The presets built into this calculator, with the letters it generates.

  1. Tap the read, write, and execute toggle buttons for each user category: owner, group, and others.
  2. View the numeric octal notation (e.g., 755) and symbolic notation (e.g., rwxr-xr-x) update in real time.
  3. Alternatively, type a numeric or symbolic permission value directly and see the toggles update.
  4. Use the preset buttons (644, 755, 600, etc.) to quickly load common file permission configurations.
  5. Copy the generated chmod command to paste directly into your terminal.

Linux File Permissions and chmod Numbers

chmod numbers such as 755 and 644 are a shorthand for Unix file permissions. Each digit sets what one group of users can do. This calculator converts between the number, the rwx letters and a ready-to-run chmod command. 755 means rwxr-xr-x: the owner can read, write and run the file, and everyone else can read and run it.

There are three sets of users: the owner, the file's group and everyone else (others). Each set can have read (r, worth 4), write (w, worth 2) and execute (x, worth 1). Add the values to get one digit: 4 + 2 + 1 = 7 for rwx, 4 + 1 = 5 for r-x and 4 + 2 = 6 for rw-. Three digits, one per set, give the full permission.

A fourth digit in front adds special bits. Setuid (4) makes a program run as its owner. Setgid (2) runs it as its group, or makes new files in a folder inherit that group. The sticky bit (1) stops people deleting other users' files in a shared folder such as /tmp. In the letters these show as s or t in the execute spot, or as a capital S or T when execute is off.

Tap the toggles, type a number such as 640, or paste letters straight from ls -l output, such as -rw-r--r--. All the views stay in sync. The tool shows the ls -l form and a chmod command with filename as a placeholder, and presets cover the common cases in the table.

A good rule: 644 for normal files, 755 for folders and scripts, 600 for private keys, and avoid 777. To run a script on a schedule, try the Crontab Generator.

Sources

Frequently Asked Questions

777 gives every user on the system read, write and execute rights. Anyone, or any compromised process, can then change or replace the file. On a web server that can let an attacker plant code. Fix the real cause instead, which is usually the wrong owner, and use chown plus 755 or 644.
644 (rw-r--r--) lets the owner read and write, and everyone else only read. 755 (rwxr-xr-x) adds execute for everyone. Use 644 for ordinary files such as HTML, images and config, and 755 for folders and for scripts or programs that need to run.
On a folder, execute means permission to enter it and reach the files inside by name. Read only lets you list the names. Without x you cannot cd into the folder or open its files, even if the files themselves allow it. That is why folders are usually 755 or 700, not 644.
Yes. Symbolic mode such as chmod +x script.sh or chmod g-w file changes only the bits you name and leaves the rest alone. A number sets all the bits at once. This tool gives you the numeric form, which is easier to repeat exactly across servers.
They mark special bits. A lowercase s in the owner or group execute spot means setuid or setgid is on and execute is also on. An uppercase S means the special bit is on but execute is off. A t in the last spot is the sticky bit with execute on, and T is the sticky bit without it.
The umask decides. Programs usually ask for 666 on files and 777 on folders, and the system then removes the bits set in your umask. The common default umask of 022 removes write for group and others, which leaves 644 and 755. A umask of 077 gives 600 and 700 instead. Run umask in a terminal to see yours.

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