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Developer & Utilities

Chmod Permissions Calculator

Calculate Linux file permissions — tick read/write/execute to get the octal chmod number, symbolic notation, and a ready-to-run chmod command. Free.

All tools
or use the checkboxes below
WhoRead (4)Write (2)Execute (1)
Owner (user)
Group
Others (world)
644
Octal
rw-r--r--
Symbolic
chmod 644 filename

💡 Quick reference

  • Read = 4, Write = 2, Execute = 1 — add them per group to get each digit.
  • 644 — files (owner edits, everyone reads). 755 — folders and scripts (owner edits, everyone reads/executes).
  • Avoid 777 on the web — it lets anyone write to the file.

Free Chmod Permissions Calculator

Calculate Linux file permissions instantly. Tick read, write, and execute for owner, group, and others to get the octal chmod number, the symbolic notation, and a ready-to-run chmod command — or type an octal value to see what it means. Free and browser-based.

What does chmod do?

chmod (change mode) sets the permissions of files and directories on Linux, macOS, and other Unix-like systems. Permissions decide who can read a file, change it, or run it. Getting them right matters for both functionality and security — too restrictive and your app breaks, too open and you expose files to anyone. This calculator translates between the checkbox view, the octal number, and the symbolic notation so you never have to do the math by hand.

How Linux permissions work

Every file has three permission groups, each with three permissions:

  • Owner (user), Group, and Others — the three groups.
  • Read (r) = 4, Write (w) = 2, Execute (x) = 1 — the three permissions.
  • Add the values within a group to get its digit (for example read + write = 6).
  • Combine the three digits into one octal number, such as 644 or 755.

How to use the chmod calculator

It works both ways:

  • Tick the read, write, and execute boxes for owner, group, and others.
  • Read off the octal number, the symbolic string, and the chmod command.
  • Or type an octal value like 755 to see exactly which permissions it grants.
  • Copy the ready-made chmod command and run it in your terminal.

Common permission values explained

A few values cover most real-world cases. 644 (rw-r--r--) is standard for files: the owner can edit, everyone else can read. 755 (rwxr-xr-x) is standard for directories and executable scripts: the owner has full control, others can read and traverse or run. 600 (rw-------) keeps a file private to its owner, ideal for config files with secrets. 700 does the same for a directory.

Security: avoid 777

Setting 777 (rwxrwxrwx) gives everyone full read, write, and execute access — a common quick fix that is also a serious security risk, especially on a web server where it lets any process or user modify your files. Almost nothing legitimately needs 777. If something is not working, the correct permission is usually 644 for files and 755 for directories, with ownership adjusted using chown rather than opening the file to the world.

Pro tip

Remember the two defaults — 644 for files, 755 for directories — and you will handle most situations correctly. When a script will not run, it usually needs the execute bit (add it to get 755). To apply permissions to a whole folder tree, use chmod with the -R recursive flag, but be careful not to make files executable unnecessarily.

FAQ

Is this chmod calculator free?
Yes. It is completely free, runs in your browser, and requires no account or sign-up.
What does chmod 644 mean?
644 means the owner can read and write (6 = 4+2), while the group and others can only read (4). In symbolic form it is rw-r--r--. It is the standard permission for regular files.
What does chmod 755 mean?
755 gives the owner read, write, and execute (7 = 4+2+1), and read and execute (5 = 4+1) to the group and others. It is the standard permission for directories and executable scripts.
How are the permission numbers calculated?
Read is 4, write is 2, and execute is 1. Add the values you want for each group (owner, group, others), then put the three digits together to form the octal value.
Is chmod 777 safe to use?
No, not on a web server or shared system. 777 lets anyone read, write, and execute the file, which is a security risk. Use 644 for files and 755 for directories instead, and fix ownership with chown if needed.
What is the difference between octal and symbolic notation?
Octal notation uses numbers like 644, while symbolic notation uses letters like rw-r--r--. They describe the same permissions. This calculator shows both at once.
How do I apply permissions to a whole folder?
Use the recursive flag: chmod -R 755 foldername. Be cautious, since applying an execute bit to every file may not be appropriate — often you want 755 for directories but 644 for files.

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