Chmod Calculator
Visual Unix permissions calculator. Select Read/Write/Execute for Owner, Group, and Others to get the numeric value and symbolic notation.
| Entity | Read (4) | Write (2) | Execute (1) | Value |
|---|---|---|---|---|
| Owner | 7 | |||
| Group | 5 | |||
| Others | 5 |
Common presets
How to use
- 1 Click the checkboxes to set Read, Write, and Execute permissions for Owner, Group, and Others.
- 2 The numeric (octal) value (e.g. 755) and symbolic notation (e.g. rwxr-xr-x) update instantly.
- 3 Or type an octal value directly to see the corresponding checkbox state.
- 4 Copy the octal value to use in chmod commands on your server.
Key features
- Click checkboxes to set read/write/execute for owner, group, and others
- Numeric octal value (e.g. 755) and symbolic notation (e.g. rwxr-xr-x) update in sync
- Type an octal value to instantly see the checkbox state
- Shows the equivalent chmod command for direct use in terminal
What is a Chmod Calculator?
In Unix-based systems (Linux, macOS), every file and directory has a set of permissions that control who can read, write, or execute it. These permissions are defined for three groups: the owner, the group, and others (everyone else). The chmod command changes those permissions.
Permissions are represented in two notations: symbolic (rwxr-xr-x) and octal (755). The octal notation sums the values for each permission bit: read = 4, write = 2, execute = 1. This calculator lets you click checkboxes and instantly see both notations and the ready-to-use chmod command.
Common Use Cases
Making scripts executable
Set 755 on shell scripts or binaries so the owner can run them and others can read them — the standard for public executables.
Securing sensitive files
SSH private keys and .env files should be 600 (owner read/write only). Many tools refuse to work if these files are world-readable.
Configuring web server files
Public web files are typically 644 (owner writes, everyone reads) and directories 755 so the server can traverse them.
Debugging "Permission denied" errors
When a process can't read or write a file, check its permissions. This tool helps you quickly work out what the current permissions allow and what you need to change.
CI/CD and Docker images
Docker entrypoint scripts and build artifacts must be executable inside the container. chmod +x (or 755) is often the fix for a failing CMD.
Learning the octal notation
Toggle checkboxes to see how r=4, w=2, x=1 add up to the octal digit for each group. A great way to build intuition for Unix permissions.
Common Permission Values
The values you'll reach for most often in everyday work.
| Octal | Symbolic | Meaning | Typical use |
|---|---|---|---|
| 777 | rwxrwxrwx | Full access for everyone | Avoid — security risk |
| 755 | rwxr-xr-x | Owner full, others read+execute | Executables, public dirs |
| 644 | rw-r--r-- | Owner read+write, others read-only | Regular files, web assets |
| 640 | rw-r----- | Owner read+write, group read-only | Configs with group access |
| 600 | rw------- | Owner read+write only | SSH keys, .env files |
| 700 | rwx------ | Owner full access, others none | Private scripts |
| 400 | r-------- | Owner read-only | Read-only credentials |