chmod Calculator
Convert Unix file permissions between checkboxes, octal, symbolic and chmod commands.
Frequently Asked Questions
What does chmod 755 mean?
The owner can read, write and execute (7), while the group and everyone else can read and execute (5). It is the usual mode for scripts, programs and directories that others need to enter but not change.
How do I calculate chmod permissions?
Add up the values for each class: read is 4, write is 2 and execute is 1. Read and write is 4+2 = 6, and read, write and execute is 7. Write one digit each for the owner, group and others, so rw-r--r-- becomes 644.
What is the difference between chmod 644 and 755?
644 lets the owner read and write and everyone else only read, which suits regular files. 755 adds execute for all three classes, which is needed to run a program or to enter a directory.
Is chmod 777 safe?
Rarely. It lets every user on the system read, modify and run the file, so a compromised account or service can overwrite it. Prefer 755 for programs, 644 for files, or a shared group with 775 or 664.
What are the setuid, setgid and sticky bits?
They add a fourth leading digit. Setuid (4) runs a program with its owner's privileges, setgid (2) runs it with its group's privileges or makes new files in a directory inherit the group, and sticky (1) stops users deleting each other's files in a shared directory like /tmp.
Does this calculator send my data anywhere?
No. It runs entirely in your browser, and the file names you type are never uploaded.
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