Chmod Calculator
Convert Unix permissions between octal, symbolic and chmod notation
| Read | Write | Execute | |
|---|---|---|---|
| Owner | |||
| Group | |||
| Other |
How to Use
- Tick the boxes — Check read/write/execute for owner, group and other in the 3x3 grid. The octal, symbolic and chmod outputs update instantly.
- Or type an octal value — Enter something like 755 in the octal field and the grid checks itself. Invalid values (digits 8-9 or more than 3 digits) are rejected with a hint.
- Use presets — One click applies common modes: 644 (web files), 755 (scripts/directories), 600 (private files), 700 (private directories), 777 (full access).
Features
- Interactive 3x3 grid — Owner, group and other crossed with read, write and execute.
- Three live outputs — Octal (755), symbolic (rwxr-xr-x) and chmod notation (u=rwx,g=rx,o=rx) at once.
- Reverse direction — Type an octal value to see which permissions it sets.
- Common presets — 644, 755, 600, 700 and 777 with a single click.
- 100% client-side — No data leaves your browser.
Use Cases
- Web deployment: Work out the right mode for uploaded files (644) and directories (755) before running chmod on the server.
- Securing credentials: Confirm that 600 gives only the owner read/write access to files like .env or SSH keys.
- Learning Unix permissions: Toggle boxes and watch how octal and symbolic notations change in real time.
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Frequently Asked Questions
What does chmod 755 mean?
chmod 755 grants the owner read, write and execute permissions (rwx), while group and others get read and execute only (r-x). It is the standard permission for executable scripts and directories on web servers.
How do I read an octal permission like 644?
Each digit is the sum of read (4), write (2) and execute (1) for one class: owner, group, other. So 644 means owner can read and write (4+2=6), while group and others can only read (4).
What is the difference between rwxr-xr-x and u=rwx,g=rx,o=rx?
Both describe the same permission set (755). The 9-character string rwxr-xr-x is the file-mode display used by ls -l, while u=rwx,g=rx,o=rx is the symbolic notation accepted by the chmod command itself.