Chmod Calculator
Calculate Linux file permissions online: tick read, write and execute or type 755 or rwxr-xr-x to get the chmod command, with setuid, sticky bit and umask.
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About the Chmod Calculator
The Chmod Calculator converts Linux and Unix file permissions between the numeric form (755), the symbolic form shown by ls -l (rwxr-xr-x) and checkboxes for owner, group and everyone else. It writes the matching chmod commands, explains what the mode allows, and covers setuid, setgid, the sticky bit and umask.
Everything runs in your browser, so your input is never uploaded to a server.
How to use the Chmod Calculator
- Tick read, write and execute for the owner, the group and everyone else, or type a mode such as 644 or rwxr-xr-x.
- Add the setuid, setgid or sticky bit if you need them.
- Enter the file or folder name and copy the chmod command.
- Check the plain-English explanation, and use the umask box to see the default modes of new files.
Common permission modes
| Mode | Symbolic | Typical use |
|---|---|---|
| 644 | rw-r--r-- | Web pages, images, config files |
| 755 | rwxr-xr-x | Scripts, programs, folders |
| 600 | rw------- | SSH private keys, secrets |
| 700 | rwx------ | Private folders such as ~/.ssh |
| 664 | rw-rw-r-- | Files a team edits together |
| 775 | rwxrwxr-x | Folders a team writes to |
| 440 | r--r----- | sudoers and read-only secrets |
| 1777 | rwxrwxrwt | /tmp: everyone writes, owners delete |
Examples
Input
755
Result
rwxr-xr-x · chmod u=rwx,g=rx,o=rx script.sh
Input
600
Result
rw------- · only the owner can read and write it (SSH refuses keys others can read)
Input
2775
Result
rwxrwsr-x · new files inherit the folder group
Input
umask 022
Result
New files 644 (rw-r--r--) · new folders 755 (rwxr-xr-x)
Common mistakes
- chmod -R 755 on everything. Recursively setting 755 makes every file executable. Use find with -type d and -type f to give folders 755 and files 644.
- Forgetting the owner. Permissions apply to the owner and group shown by ls -l. If the web server runs as another user, change ownership with chown rather than opening the mode to everyone.
Works well with the Chmod Calculator
- Decimal to Binary Converter: see each permission digit as three bits.
- Cron Expression Parser: schedule the script you just made executable.
- Subnet Calculator: plan the network of the same server.
Frequently asked questions
What does chmod 755 mean?
The owner can read, write and execute (7 = 4 + 2 + 1), and the group and everyone else can read and execute (5 = 4 + 1). It is the usual mode for scripts, programs and web folders.
What does chmod 644 mean?
The owner can read and write (6 = 4 + 2), and everyone else can only read (4). It is the usual mode for web pages, images and configuration files.
Is chmod 777 safe?
Rarely. 777 lets every user on the system change or replace the file, which attackers use to plant code on web servers. Fix ownership with chown and use 755 or 775 instead.
What does execute mean on a folder?
On a directory, x allows entering it and reaching the files inside, r allows listing the names and w allows creating, renaming and deleting files. A folder needs x for anything inside it to be usable.
What is the fourth digit, as in 2775?
The first digit holds the special bits: 4 setuid, 2 setgid and 1 sticky. 2775 is a shared folder where new files keep the folder's group; 1777 is /tmp, where only owners can delete their files.
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