Chmod Octal Calculator Online
Toggle permission checkboxes and see the corresponding octal value update in real time. This calculator runs entirely in your browser with no server interaction.
Chmod Calculator
Calculate Unix file permissions. Toggle checkboxes or enter an octal code — results update instantly.
| Role | Read | Write | Execute | Value |
|---|---|---|---|---|
| Owner | 6 | |||
| Group | 4 | |||
| Others | 4 |
Common Presets
About Unix File Permissions
- Each digit represents permissions for owner, group, and others.
- Read (
4) + Write (2) + Execute (1) = octal digit. - Example:
755= owner rwx, group rx, others rx. - Everything runs in your browser — no data is sent over the network.
What is chmod octal notation?
Chmod octal notation uses three digits (e.g., 755) to represent file permissions. Each digit is the sum of permission values: read (4), write (2), and execute (1). The first digit is the owner, the second is the group, and the third is others. So 755 means the owner can read, write, and execute (7), while group and others can read and execute (5).
Common use cases
The most common octal values are 644 (owner read-write, everyone else read-only — typical for files), 755 (owner full, everyone else read-execute — typical for directories and scripts), and 600 (owner read-write only — typical for SSH keys and secrets). Knowing these by heart saves time in daily server administration.
Frequently Asked Questions
What does chmod 777 mean?
chmod 777 grants read, write, and execute permissions to everyone — owner, group, and others. This is generally considered a security risk and should be avoided in production. Use more restrictive permissions like 755 or 644 instead.
What chmod should I use for SSH keys?
SSH private keys should be chmod 600 (read-write for owner only). SSH will refuse to use a key file with permissions that are too open. The .ssh directory itself should be 700.