Chmod Calculator
Calculate Unix file permissions. Toggle read, write, execute for owner, group, and others.
Chmod Calculator - Unix File Permissions Calculator Online
Calculate Unix file permissions visually. Toggle checkboxes and get the chmod command with octal and symbolic notation.
Toggle the read, write, and execute checkboxes for owner, group, and others to build your desired permission set. The calculator displays the octal notation (like 755 or 644) and symbolic notation (like rwxr-xr-x) in real-time. Copy the generated chmod command directly—for example, chmod 755 filename. The tool also works in reverse: paste an octal code to see which checkboxes correspond to those permissions. A reference section explains what each permission type allows for files vs. directories. All calculations happen instantly in your browser.
Linux administrators set correct permissions on web server files—755 for directories, 644 for files—to balance accessibility and security. Developers troubleshoot permission denied errors by calculating what permissions their script or user actually needs. DevOps engineers preparing deployment scripts verify that executables have the correct permission bits set. Students learning Unix file systems use the calculator to understand how octal codes translate to actual access rights.
Directories need execute permission for users to access files inside them—755 is standard for web-accessible directories. The 777 permission (read/write/execute for everyone) is a security risk; avoid it unless you're debugging a specific permission issue temporarily. Symbolic notation (chmod u+x) is safer for scripts because it doesn't overwrite existing group/other permissions. When setting permissions for SSH keys, 600 (owner read/write only) is required—more permissive settings cause authentication to fail. Use 644 for world-readable files like HTML/CSS and 600 for sensitive config files.
All processing happens directly in your browser. Your files never leave your device — no server uploads, no cloud storage, no data retention. The tool works offline once loaded, requires no registration, and is completely free with no usage limits.
Frequently Asked Questions
What does chmod 755 mean?
Owner can read, write, execute (7). Group and others can read and execute but not write (5).
What is the difference between 644 and 755?
644 gives owner read/write, others read-only. 755 adds execute permission, typically used for directories and scripts.
When should I use 777?
Almost never in production. 777 gives full permissions to everyone, which is a security risk. Use it only for temporary testing.