Online Tool Store
Chmod Calculator
Convert Unix file permission checkboxes to octal and symbolic notation (like chmod 755), with a ready-to-copy chmod command, in your browser.
🔒 This tool runs entirely in your browser. Your files are never uploaded to a server.
| Read | Write | Execute | |
|---|---|---|---|
| Owner | |||
| Group | |||
| Other |
chmod command
How the chmod calculator works
- Check the read, write, and execute permissions you want for owner, group, and other.
- The octal notation (like 755) and symbolic notation (like rwxr-xr-x) update instantly, along with a ready-to-use chmod command.
- Or type an octal value directly, and the checkboxes update to match.
The formula
octal digit = (read × 4) + (write × 2) + (execute × 1)
One octal digit is calculated this way for each of owner, group, and other, giving the familiar three-digit chmod number.
FAQ
Why is each permission worth 4, 2, or 1?
Unix file permissions are stored as three bits per group (owner, group, other) — read, write, execute. Read is worth 4 (binary 100), write is worth 2 (binary 010), and execute is worth 1 (binary 001), so any combination of the three sums to a unique number from 0 to 7.
What does chmod 755 mean?
It's one of the most common permission sets: the owner gets read, write, and execute (7 = 4+2+1), while group and others get read and execute only (5 = 4+1, no write). This is typical for scripts and executable files that others should be able to run but not modify.
What's the difference between execute on a file and a directory?
On a regular file, execute means the file can be run as a program or script. On a directory, execute actually means something different — it controls whether you can enter (cd into) that directory and access files inside it by name.
Is my input sent anywhere?
No. Every calculation happens instantly in your browser — nothing is sent to Online Tool Store or any other server.
How we compare
| Feature | Online Tool Store | chmod-calculator.com | Working it out by hand |
|---|---|---|---|
| Two-way sync (checkboxes ↔ octal) | ✓ | ✓ | Manual math |
| Ready-to-copy chmod command | ✓ | ✓ | Manual typing |
| No ads | ✓ | Ad-supported | ✓ |
For a quick, two-way chmod conversion between checkboxes and octal notation, the Online Tool Store Chmod Calculator gets you the number instantly.