Calculate Unix file permissions — octal, symbolic, and the chmod command.
Calculate Unix file permissions visually: toggle read/write/execute for owner, group, and others to get the octal value (like 755), the symbolic string (rwxr-xr-x), and a ready-to-run chmod command. Type an octal value to reverse it. Runs in your browser.
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Owner, group, then everyone else. Each digit sums read (4), write (2) and execute (1), so 7 is all three, 5 is read and execute, 0 is none. 755 therefore means the owner can do everything while others can read and run but not modify — the standard for directories and executables.
It grants write access to every user on the system, so anyone can modify or replace the file. On a web server that can mean an attacker overwriting your scripts. It is a common "fix" for permission errors that trades a small problem for a serious vulnerability — set the correct owner instead.
On a directory, execute means the ability to traverse into it and access what is inside. Read without execute lets you list the names but not open anything, which produces confusing permission-denied errors. This is why directories are normally 755 while ordinary files are 644.
Yes, Chmod Calculator is completely free. No signup, no account, and no watermark on outputs. A Pro tier is available for 100 AI ops/day and larger file sizes.
Chmod Calculator runs entirely in your browser. Your file is never uploaded — it is read, processed and saved locally, so it never reaches our servers or anyone else's. You can disconnect from the internet after the page loads and it still works.
| Permission | Owner | Group | Others |
|---|---|---|---|
Read r | |||
Write w | |||
Execute x |
chmod 755 filenameOwner: read, write, execute · Group: read, execute · Others: read, execute
How permissions work: Every file has three permission sets — owner, group, and others — each with read (r=4), write (w=2), and execute (x=1). Adding the values per set gives the octal digit, so rwx = 7 and r-x = 5.
Common values: 644 for files (owner writes, everyone reads), 755 for directories and scripts (owner writes, everyone reads and executes), 600 for private files like SSH keys.
Privacy: Everything is calculated locally in your browser. Nothing is uploaded.