Advertisement
Guide
About the Chmod Calculator
On Unix and Linux systems, every file and directory has permissions that control who can read, write, and executeit. Those permissions are split across three groups — the file's owner, its group, and others (everyone else). The chmod command changes them, and this calculator translates between the clickable rwx view, the octal number like 755, and symbolic notation like rwxr-xr-x.
Toggle the boxes and read off the number, or type a number and see which permissions it grants — plus the exact command to run.
How the numbers work
Each permission is a value: read = 4, write = 2, execute = 1. Add them up per group to get one digit (0–7). So 7 is read+write+execute (4+2+1), 5 is read+execute (4+1), and 6 is read+write (4+2). Three digits — owner, group, others — make a full mode like 644 or 755.
Common permission sets
644— files: owner can edit, everyone can read. The typical default for documents and web files.755— directories and scripts: owner can edit, everyone can read and enter/run.600— private files like SSH keys: only the owner can read or write.700— private directories: only the owner has any access.
How to use it
- 1Click the read, write, and execute boxes for owner, group, and others.
- 2Read the resulting octal (e.g. 755) and symbolic (rwxr-xr-x) values.
- 3Or type an octal number to see which permissions it represents.
- 4Copy the generated chmod command and run it in your terminal.
Frequently asked questions
What does chmod 755 mean?
The owner has read, write, and execute (7); the group and others have read and execute (5 and 5). It is the standard mode for directories and executable scripts.
What is the difference between 644 and 755?
644 grants no execute permission — good for regular files. 755 adds execute for everyone, which directories need to be entered and scripts need to run.
How do read, write, and execute map to numbers?
Read is 4, write is 2, and execute is 1. You add them per group, so read+write+execute is 7 and read+execute is 5.
What does execute mean on a directory?
On a directory, the execute bit lets you enter it and access files inside by name. Without it, you cannot traverse into the directory even if you can read its listing.
What is the difference between symbolic and octal chmod?
They express the same permissions two ways. Octal (755) sets all bits at once; symbolic (u+x, go-w) adjusts specific bits relative to the current state. This tool shows both.