Chmod Calculator

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More About Chmod Calculator

Chmod Calculator converts Unix/Linux file permissions between the symbolic form (rwxr-xr-x) and the octal number used with chmod (like 755), with checkboxes for read, write, and execute across owner, group, and others.

The octal system clicks once you see the arithmetic: each of the three digits covers one group, owner, group, others, and is the sum of read (4), write (2), and execute (1). So 7 is all permissions, 5 is read+execute, 6 is read+write, and a number like 755 reads as 'owner everything, group and others read+execute'. The calculator shows both notations live so you can learn by toggling.

Two everyday values dominate: 644 (rw-r--r--) for regular files, where the owner edits and others read, and 755 (rwxr-xr-x) for directories and executables. A subtlety worth knowing is that 'execute' on a directory means the right to enter and traverse it, which is why folders need 755, not 644.

A security note the tool encourages: avoid 777 (full access for everyone) on servers, as it lets anyone modify the file and is rarely truly needed, set the minimum permissions instead. Everything runs in your browser with nothing uploaded. Pair it with the other ToolsMonk developer tools for your sysadmin and web tasks.

Chmod Calculator at a glance
PriceFree, no signup, no paywall, no watermark
Works onAny modern browser: desktop, tablet, and mobile
ProcessingIn your browser, files never leave your device
Account requiredNone
CategoryDeveloper Tools

Using Chmod Calculator, Step by Step

Toggle read, write, and execute for owner, group, and others

The octal number (e.g. 755) and symbolic notation (rwxr-xr-x) update live

Or enter an octal number to see what it permits

Copy the chmod value for your command

Chmod Calculator Features & Benefits

Converts Unix file permissions between symbolic (rwx) and octal (e.g. 755)

Toggle read/write/execute for owner, group, and others

Shows the matching chmod number and symbolic notation

Explains what each permission set allows

Runs in your browser, nothing is uploaded

Free, with no signup and no rate limit

Common Chmod Calculator Use Cases

Working out the chmod number for a set of permissions

Decoding what a permission like 644 or 755 actually means

Setting correct permissions for web files and scripts

Learning Unix/Linux file permissions

Getting the Best Out of Chmod Calculator

  • Rule of thumb: 644 for files, 755 for directories and scripts

  • Avoid 777 on web servers, it's a security risk and rarely necessary

  • Each digit = read(4) + write(2) + execute(1) for owner / group / others

Frequently Asked Questions About Chmod Calculator

Common questions about this tool, its workflow, and what to expect before you use it.

Tick read, write and execute for owner, group and others, or type an octal number, and the Chmod Calculator shows the numeric command, the symbolic command and an ls -l style preview together. Each value can be copied, so you can paste the exact chmod command into your terminal.

755 gives the owner read, write and execute, and gives the group and everyone else read and execute. It is the usual setting for directories and executable scripts. Each digit adds read as 4, write as 2 and execute as 1, so 7 is 4 plus 2 plus 1 and 5 is 4 plus 1.

The calculator offers one-click presets: 644 for regular files and web assets, 755 for executables and directories, 600 for SSH keys and secrets, 700 for private scripts, 775 for group-writable folders, 444 for read-only, 777 for fully open access and 1777 for a shared folder like /tmp.

They are special permission bits shown as a fourth leading digit. Setuid (4) runs a file as its owner, setgid (2) runs it as its group or makes new files in a folder inherit the group, and sticky (1) stops users deleting each other's files in a shared folder. Toggle them to see the full four-digit value.

777 lets every user on the system read, write and execute the file, so any account or compromised process can change it. The calculator rates each combination with a security label and flags world-writable settings. Use the narrowest permission that works, typically 644 for files and 755 for folders on a web server.

Standards and references for Chmod Calculator

  • chmod (POSIX.1-2024)

    The Open Group

    Defines the symbolic and octal permission modes the calculator converts between.

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Chmod Calculator
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