Chmod Calculator
Visually set Unix file permissions and instantly see octal and symbolic notation.
Common Presets
| Entity | Read (4) | Write (2) | Execute (1) | Value |
|---|---|---|---|---|
| Owner (u) | 4+2+0 | |||
| Group (g) | 4+0+0 | |||
| Others (o) | 4+0+0 |
Octal
644
Symbolic
-rw-r--r--
How to Use
- 1. Click the r, w, x buttons to toggle permissions for Owner, Group, and Others.
- 2. The octal value and symbolic notation update instantly.
- 3. Use the preset buttons (755, 644, etc.) to jump to common configurations.
- 4. Copy the octal or symbolic value, or use the shown chmod command directly in your terminal.
About Chmod Calculator
Unix file permissions control who can read, write, and execute files on Linux, macOS, and other Unix-like systems. Every file and directory has three sets of permissions: for the owner (the user who created the file), for the group (a set of users), and for others (everyone else).
Each permission set has three bits: read (r = 4), write (w = 2), and execute (x = 1). The octal value for a permission set is the sum of the active bits. For example, read + write = 4 + 2 = 6. The full octal string like "755" is three such digits: owner=7 (rwx), group=5 (r-x), others=5 (r-x).
The symbolic notation (-rwxr-xr-x for 755) shows the same information in a more human-readable form, where each - means the permission is not set. This is what you see when you run ls -la in a terminal.
Our chmod calculator lets you toggle permissions visually and instantly see both representations. It also shows the exact chmod command you need to run in your terminal, so you can copy and paste without memorizing the octal math.
You may also find our Hash Generator, UUID Generator, and Cron Generator helpful.
Frequently Asked Questions
What does chmod mean?
chmod stands for "change mode". It is a Unix/Linux command used to set the read, write, and execute permissions for a file or directory for the owner, group, and others (world).
What does 755 mean?
755 means the owner has read, write, and execute (7 = 4+2+1), while group and others each have read and execute only (5 = 4+0+1). This is the standard permission for executable scripts and web directories.
What does 644 mean?
644 means the owner has read and write (6 = 4+2), while group and others have read only (4). This is the standard permission for regular files like HTML, CSS, and config files.
Why should I avoid 777?
777 grants read, write, and execute to everyone — including other users on the system and potentially web processes. This is a security risk on shared servers and should generally be avoided in production.
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