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 a 3- or 4-digit octal number directly, special bits included, 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 a 3- or 4-digit octal value such as 755 or 4755 to fill the grid instantly
Builds a ready-to-copy command like chmod 644 file; replace "file" with your path
Shows the full 9-character symbolic permission string like rwxr-xr-x
Handles setuid, setgid and the sticky bit, shown as s, S, t or T exactly like ls -l
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, plus setuid, setgid or sticky if you need a special bit.
Read the resulting octal value and symbolic rwx string shown below the grid.
Or type an octal number such as 644 or 4755 into the Octal field, or paste a string from ls -l into the Symbolic field.
Copy the generated command, replace "file" with your file's path, and run it in your terminal.
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, because the type flag from ls -l is not part of the chmod mode. You can still paste a full ls -l string such as drwxr-xr-x; the type letter is ignored.
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.
Seeing a capital S or T, as in rwSr--r--. — An uppercase S or T means a special bit is set but the execute bit under it is not, which is usually a mistake: 4644 shows as rwSr--r--. Tick Execute for that class to get a lowercase s or t, as in 4755 (rwsr-xr-x).
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?
Yes. Tick Setuid (4), Setgid (2) or Sticky (1), or type a 4-digit mode such as 4755, 2775 or 1777. The symbolic string shows them the way ls -l does, as s or t in an execute slot (S or T when execute is off), and the command becomes chmod 4755 file.
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.
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