Chmod Calculator
Convert Unix file permissions between octal and symbolic (rwx).
Your permission values are processed locally in your browser and nothing is uploaded to a server.
Setting up a repo? Try the .gitignore Generator.
About Chmod Calculator
This chmod calculator converts Unix and Linux file permissions between octal and symbolic rwx notation without making you memorize the math. Toggle the read, write, and execute checkboxes for owner, group, and others and instantly see the matching octal value (like 644 or 755), the symbolic string (rw-r--r--), and the exact chmod command to paste into your terminal. You can also type an octal number directly and watch the permission grid update in real time. Built for developers, sysadmins, and DevOps engineers setting file modes on servers, deploy scripts, SSH keys, and web directories, it doubles as a quick reference when you are decoding what chmod 644 means or building a unix file permissions string from scratch. Everything runs entirely in your browser, so your input is processed locally and never leaves your device.
Features
- Interactive permission grid for owner, group, and others across read, write, and execute
- Live two-way conversion between octal (e.g. 755) and symbolic rwx notation
- Type an octal value directly to populate the checkbox grid instantly
- Generates the ready-to-copy chmod command for your target file
- Shows the full 9-character symbolic permission string like rwxr-xr-x
- Supports 3-digit and 4-digit octal input for standard and special modes
- Updates results live as you toggle checkboxes, with no submit step
How to use the Chmod Calculator
- Check the read, write, and execute boxes for owner, group, and others to match the access you want.
- Read the resulting octal value and symbolic rwx string shown below the grid.
- Or type an octal number such as 644 into the Octal field to update the grid automatically.
- Copy the generated chmod command and run it in your terminal against your target file.
Example
Input
rw-r--r--
Output
644
chmod 644 file
Symbolic owner read/write with group and others read-only maps to octal 644.
Common errors & troubleshooting
- Typing a digit above 7 in the octal field, such as 844. — Each permission digit must be 0-7 because it is the sum of read (4), write (2), and execute (1). Use values like 644 or 755.
- Expecting a leading file-type character like d or - in the symbolic output. — The tool shows the 9-character permission string (rwxr-xr-x) only. The leading type flag from ls -l is not part of the chmod mode.
- Confusing 777 as a safe default for web files. — 777 grants write and execute to everyone, which is a security risk. Use 644 for files and 755 for directories or scripts in most cases.
- Pasting a 4-digit mode and ignoring the leading digit. — The leading digit covers setuid, setgid, and the sticky bit. This calculator focuses on the last three permission digits, so verify special bits separately.
- Wondering why chmod 644 leaves a script non-executable. — 644 has no execute bit. Use 755 (rwxr-xr-x) so the owner can run the script while group and others can read and execute it.
Frequently asked questions
- What is a chmod calculator and what does it do?
- A chmod calculator converts Unix file permissions between octal numbers (like 644) and symbolic rwx notation (like rw-r--r--). This one also generates the exact chmod command so you can apply the mode in your terminal.
- What does chmod 644 mean?
- 644 gives the owner read and write (rw-), and the group and others read-only (r--). In the chmod calculator this shows as the symbolic string rw-r--r--, common for regular files.
- How do I convert symbolic permissions like rwxr-xr-x to octal?
- Toggle the matching read, write, and execute boxes in the grid and the chmod calculator displays the octal value, in this case 755. Each digit is the sum of read (4), write (2), and execute (1).
- When should I use 755 versus 644?
- Use 755 for directories and executable scripts so they can be entered or run, and 644 for normal files that should not be executable. The calculator generates the exact chmod command for either.
- Does the chmod calculator handle setuid, setgid, or the sticky bit?
- It focuses on the standard owner, group, and others permissions. You can enter 4-digit octal values, but the special-bit leading digit should be confirmed separately.
- Is my permission input kept private in the chmod calculator?
- Yes. The chmod calculator runs entirely in your browser, so the values you enter are processed locally and never leave your device, with no tracking.
Related tools
All ArrayKit tools