Chmod Calculator
DeveloperCalculate Linux file permissions with an interactive chmod calculator. Convert between numeric and symbolic notation.
Permissions
Common Permissions
What is This Tool?
A chmod calculator converts between symbolic (rwxr-xr-x) and numeric (755) Unix file permission formats. Toggle read, write, and execute permissions for owner, group, and others with a visual grid, and get the equivalent chmod command instantly.
Unix permissions use three permission sets (owner, group, others) with three bits each (read=4, write=2, execute=1). The numeric format sums these bits: 755 = rwx(7) r-x(5) r-x(5). Special bits include setuid (4000), setgid (2000), and sticky bit (1000).
Common Use Cases
Server Administration
Calculate correct file permissions for web servers, SSH keys, configuration files, and deployment scripts.
Security Hardening
Set minimum required permissions for sensitive files — private keys (600), scripts (755), config (644).
Docker & Containers
Set correct file permissions in Dockerfiles and container builds where permission issues cause runtime failures.
CI/CD Debugging
Debug "permission denied" errors in build pipelines by understanding and correcting file permission settings.
Frequently Asked Questions
What does 755 mean?
Owner: read+write+execute (7). Group: read+execute (5). Others: read+execute (5). Common for directories and scripts.
What permissions should SSH keys have?
Private keys: 600 (owner read+write only). Public keys: 644. SSH directory: 700. SSH will refuse to use keys with loose permissions.
What are setuid/setgid/sticky?
Setuid (4000): runs as file owner. Setgid (2000): runs as group/inherits directory group. Sticky (1000): only owner can delete files in directory (e.g., /tmp).