Calculate Linux file permissions
| Permission | Owner | Group | Others |
|---|---|---|---|
| read | r | r | r |
| write | w | - | - |
| execute | x | x | x |
The Chmod Calculator converts Linux and Unix file permissions between the symbolic notation you see in ls -l (like rwxr-xr-x) and the three-digit octal codes you pass to the chmod command (like 755). Toggle the read, write, and execute checkboxes for the owner, group, and other classes, and the tool instantly shows both the octal value and the ready-to-run chmod command.
It is built for developers, sysadmins, and DevOps engineers who set permissions on scripts, web directories, SSH keys, and deployment files, and who would rather click boxes than do the bit math in their head. Everything runs in your browser, so it doubles as a quick reference when you cannot remember whether 644 or 640 is what you actually want.
Linux permissions are grouped into three classes, applied in this order: owner, group, and other. Each class has three permission bits, worth 4 for read (r), 2 for write (w), and 1 for execute (x). You add the values of the bits you want within a class to get a single digit from 0 to 7. For example, read plus write plus execute is 4 + 2 + 1 = 7, read plus execute is 4 + 1 = 5, and read plus write is 4 + 2 = 6. Concatenating the three digits gives the familiar octal code, so rwxr-xr-x becomes 755 and rw-r--r-- becomes 644.
An optional leading fourth digit holds the special bits: setuid (4), setgid (2), and the sticky bit (1), combined the same way. That is why a shared, world-writable directory like /tmp is often set to 1777 (sticky bit plus rwx for everyone), and an executable that runs with its owner's privileges may use 4755. Common everyday values are 644 for normal files, 755 for scripts and directories, 600 for private keys, and 700 for private directories. The calculator simply performs this bit arithmetic both ways so you never have to convert between the symbolic and octal forms manually.
644 (rw-r--r--) gives the owner read and write while everyone else only reads, which suits regular files. 755 (rwxr-xr-x) adds the execute bit for all three classes, which is what you want for scripts and directories that need to be entered or run.
On a directory the execute bit means permission to traverse it, that is, to access files and subdirectories inside. Without execute, you cannot cd into the directory or reach its contents even if you have read permission, which is why directories are usually 755 rather than 644.
Use 600 (rw-------) so only the owner can read and write it. Most SSH clients refuse to use a private key that is readable by group or other, so 640 or 644 will trigger a permissions-too-open error.
They are the special fourth-digit bits. Setuid (4) makes an executable run as its owner, setgid (2) makes files inherit the directory's group or runs a program as its group, and the sticky bit (1) on a directory lets only a file's owner delete it, as used on /tmp with 1777.
No. It only generates the octal value and the chmod command text for you to copy. You must run the command yourself in a terminal on your own system; the tool never touches your files.
Yes, it is completely free with no sign-up. All calculations happen locally in your browser using simple math, so nothing you enter is uploaded, stored, or sent to any server.
Break 750 into 7, 5, 0. Seven is rwx (owner), five is r-x (group), and zero is --- (other), giving rwxr-x---. The calculator shows this symbolic string automatically as you enter the octal code.