| Class | Read | Write | Execute |
|---|---|---|---|
| Owner | |||
| Group | |||
| Others |
0644
rw-r--r--
chmod 0644 filename- Owner can read, write.
- Group can read.
- Others can read.
What is the Chmod Calculator?
The Chmod Calculator converts Unix and Linux file permissions between the three forms the chmod command understands: the numeric octal mode such as 755, the symbolic mode such as rwxr-xr-x, and individual read, write and execute checkboxes for the owner, the group and everyone else. Change any one representation and the other two update instantly, so you can move from a permission string in a tutorial to the exact chmod command you need to run without doing octal arithmetic in your head.
Every file and directory on a POSIX system carries permissions for three classes of user. The owner is the account that owns the file, the group is a set of users who share access, and others is everyone else. Each class has three bits: read, write and execute. Read allows viewing a file or listing a directory, write allows changing a file or adding and removing entries in a directory, and execute allows running a file as a program or entering a directory. The calculator maps each bit to a checkbox so you can see exactly what a mode grants.
Numeric mode encodes each class as a single octal digit, because read is worth 4, write is worth 2 and execute is worth 1, and those values add up uniquely from 0 to 7. So 7 is read, write and execute, 5 is read and execute, and 4 is read only. The three digits of 755 therefore mean the owner has full access while the group and others can read and execute but not write. The tool also handles the fourth, leading digit for the special bits: setuid, setgid and the sticky bit, which appear as the s and t characters in a symbolic listing.
Everything runs entirely in your browser. There is no signup, nothing is uploaded, and the tool keeps working offline once the page has loaded. It is equally useful as a quick converter when you are following a deployment guide, as a learning aid for understanding how ls -l output maps to chmod numbers, and as a sanity check before you set permissions on a server, where getting a mode wrong can lock you out of a file or expose it to the whole system.
How to use the Chmod Calculator?
Toggle the permissions
Check read, write and execute for the owner, group and others to build the mode you want.
Or enter a mode
Type an octal mode like 755 or a symbolic mode like rwxr-xr-x and the checkboxes update to match.
Add special bits
Turn on setuid, setgid or the sticky bit if you need them; the leading octal digit updates automatically.
Copy the chmod command
Copy the ready-made chmod command or the octal and symbolic values and use them on your system.
Key Features
Three-way conversion
Octal, symbolic and rwx checkboxes stay in sync; edit any one and the others update.
Special bits
Full support for setuid, setgid and the sticky bit, shown as s, S, t and T like ls -l.
Ready chmod command
A copy-ready chmod command is generated for the current mode so you can paste it into a terminal.
Plain-English summary
A written description spells out exactly what each class can do for the selected mode.
Frequently Asked Questions
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