BYTETOOLS

Chmod Calculator

Convert Linux file permissions between rwx checkboxes, octal values like 755 and symbolic strings — with setuid, setgid and sticky bit support. Free tool.

Permissions

ClassRead (4)Write (2)Execute (1)Digit
Owner7
Group5
Others5
755
Octal mode
rwxr-xr-x
Symbolic (ls -l)

Commands

chmod 755 filename

chmod u=rwx,g=rx,o=rx filename

What is the Chmod Calculator?

The ByteTools Chmod Calculator converts Linux and Unix file permissions in both directions: tick the read, write and execute boxes for owner, group and others to get the octal number, or type an octal value like 755 to see exactly which permissions it grants.

  • Two-way conversion: checkboxes to octal and octal to checkboxes
  • Supports setuid, setgid and sticky bits (4-digit modes like 4755)
  • Shows the symbolic ls -l string, e.g. rwxr-xr-x
  • Generates numeric and symbolic chmod commands
  • Quick presets for common modes: 755, 644, 700, 777
  • 100% client-side bit math — nothing is uploaded

How to use the Chmod Calculator

  1. 1

    Tick the read, write and execute boxes for owner, group and others — or type an octal value like 644.

  2. 2

    Optionally enable setuid, setgid or the sticky bit.

  3. 3

    Read the resulting octal mode and the symbolic ls -l string.

  4. 4

    Copy the generated chmod command and run it on your file or directory.

About the Chmod Calculator

The ByteTools Chmod Calculator converts Linux and Unix file permissions in both directions: tick the read, write and execute boxes for owner, group and others to get the octal number, or type an octal value like 755 to see exactly which permissions it grants.

It also handles the three special bits — setuid, setgid and the sticky bit — and shows the full picture every way you might need it: the octal mode, the symbolic ls -l string such as rwxr-xr-x, and ready-to-run chmod commands in both numeric and symbolic form.

All of the bit math happens locally in your browser, so it is a fast, private way to double-check a permission before you run chmod on a production server.

Frequently asked questions

What does chmod 755 mean?

755 gives the owner read, write and execute (7 = 4+2+1), while group and others get read and execute (5 = 4+1). In symbolic form that is rwxr-xr-x — the standard mode for directories and executable scripts.

What is the difference between 644 and 755?

644 (rw-r--r--) lets the owner read and write while everyone else can only read — right for ordinary files. 755 adds execute permission for everyone, which is needed for directories (to enter them) and for scripts or binaries.

How do the numbers in an octal mode work?

Each digit is the sum of read = 4, write = 2 and execute = 1 for one class of user: first digit owner, second group, third others. So 6 means read + write, 5 means read + execute, and 7 means all three.

What are setuid, setgid and the sticky bit?

They are the optional fourth (leading) octal digit: setuid (4) runs an executable as the file's owner, setgid (2) runs it as the group or makes new files in a directory inherit its group, and the sticky bit (1) stops users deleting each other's files in shared directories like /tmp, which is mode 1777.

Why does ls -l show a capital S or T?

A lowercase s or t means the special bit is set together with execute permission. A capital S or T warns that the special bit is set but execute is not — usually a misconfiguration, since the special bit has no effect without execute.

Is chmod 777 safe to use?

Rarely. 777 lets every user on the system read, modify and execute the file, which is a common security hole. Prefer 755 for directories and executables and 644 for regular files, and only widen permissions when you have a specific reason.

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