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Chmod Calculator

Calculate Linux/Unix file permissions visually. Convert between octal (755) and symbolic (rwxr-xr-x) notation instantly.

Guide: How to use & features

  • Select permissions for "Owner", "Group", and "Others" using the checkboxes.
  • The corresponding chmod command is generated in real-time in the output area.
  • You can also input an octal number to see the matching visual permissions.

Samples: Sample input & output

Calculate 755 (rwxr-xr-x)

Input

Owner: Read, Write, Execute
Group: Read, Execute
Others: Read, Execute

Output

chmod 755

FAQ: FAQ

  • How do octal numbers (like 755) map to rwx symbols?

    Each digit represents the permissions for owner, group, and others, summing read r=4, write w=2, and execute x=1. So 7 is 4+2+1 = rwx and 5 is 4+1 = r-x; 755 means owner rwx, group r-x, others r-x. This tool converts between the two with a quick check.

  • When should I use 755 versus 644?

    755 suits directories and scripts that need to be executable, while 644 suits ordinary files that do not (HTML, configs, images). The safe default is "755 for directories, 644 for files," and not granting unneeded write or execute permission is a security basic.

  • Will setting 777 just fix my permission problems?

    It may work temporarily, but it is not recommended. 777 lets anyone read, write, and execute, which is a serious risk, especially on a public server. First check whether the right ownership (chown) plus the minimum permissions (often 755 or 644) solves it.

Use cases: Common use cases

  • Server setup permissions

    Quickly calculate recommended permissions for web directories and sensitive files.

  • Debugging access issues

    Visually match current octal values against intent to fix "Permission Denied" errors.

  • Security auditing

    Double-check if permissions are too loose (like world-writable) on a clean GUI.

Notes: Notes & limitations

  • Root Privileges

    Modifying system file permissions may require sudo. Pay attention to your execution environment.

  • Security Risks

    Setting open permissions like "777" can be a security risk. Use the most restrictive permissions necessary.
chmod 755 filename
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Owner Group Public
Read (4)
Write (2)
Execute (1)

Special Bits

chmod Permission Calculator

Linux file permissions can be written as numeric modes such as 755, symbolic values such as rwxr-xr-x, or chmod commands. This calculator helps translate between permission formats so you can review access before applying it to scripts, files, or directories.

Common use cases

  • Understand numeric modes: Translate 644, 755, 600, and similar values into readable permissions.
  • Review deployment commands: Check chmod values before changing server files.
  • Explain permissions: Share clear owner, group, and others permission details in documentation or tickets.

Security note

Avoid broad permissions such as 777 unless you fully understand the environment and risk. Write access for everyone can create serious security problems on shared systems.

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