Chmod Calculator

Chmod calculator for Linux file permissions

Convert Linux and Unix file permissions between octal and symbolic notation. Select read, write, and execute access for the owner, group, and others, or type a mode directly. The calculator also handles setuid, setgid, and sticky bits and builds a copyable chmod command entirely in your browser.

How do I calculate a chmod value?

Choose the permissions needed by each user class. Read has a value of 4, write has a value of 2, and execute has a value of 1. Add the selected values within the owner, group, and others columns. For example, read plus write is 6, while read plus execute is 5, producing 0755 for rwxr-xr-x.

What do chmod numbers such as 644 and 755 mean?

Each of the final 3 digits represents one user class: owner, group, and others. 0644 gives the owner read and write access while everyone else can only read. 0755 gives the owner full access and gives the group and others read and execute access. The leading digit represents special bits and is usually 0.

Can I convert symbolic permissions to octal?

Yes. Enter a 9-character symbolic mode such as rw-r----- and the octal value, checkboxes, and command update immediately. You can also edit the octal field to convert in the other direction. Invalid modes remain visible with a correction message so you can finish editing without losing your input.

What are setuid, setgid, and the sticky bit?

Setuid lets an executable run with its owner's effective identity. Setgid applies the file's group identity to executables and makes new items inherit a directory's group. On shared directories, the sticky bit limits deletion or renaming to the file owner, directory owner, or root. These special modes should be enabled only when their behavior is intended.

Why does the symbolic value show S or T instead of s or t?

Lowercase s and t mean the related execute bit is also enabled. Uppercase S or T means the special bit is set while that execute bit is off. The calculator applies this distinction automatically when you toggle execute access or edit symbolic notation.

How do I use the generated chmod command?

Enter the target file or directory path, copy the generated command, and run it in a shell where you have permission to change that target. Paths containing spaces or apostrophes are safely quoted. Review the selected rights before running the command, especially broad modes such as 0777.

Is chmod 777 safe?

0777 lets every user read, modify, and execute the target, so it is rarely the right long-term fix for an access problem. Prefer the narrowest permissions your application needs, such as 0644 for many regular files, 0755 for public directories or executables, and 0700 for private content.