Convert Linux file permissions between octal, symbolic and checkboxes. Nothing is uploaded.

How the chmod calculator works

Linux file permissions are three groups of three bits. Read is worth 4, write is 2 and execute is 1, and the bits for one role add up to a single octal digit. The three digits stand for the owner, the group and everyone else, so 755 means rwxr-xr-x and 644 means rw-r--r--. This page keeps all three views in step: edit the octal value, the symbolic string or the checkboxes and the others follow. A four-digit value sets the special bits, where the leading digit is setuid (4), setgid (2) and sticky (1). For other text tasks see the text case converter and the all tools page.

Frequently asked questions

What do the numbers mean?
Each role has three bits: read is 4, write is 2 and execute is 1. Adding the bits gives one octal digit, and the three digits cover owner, group and others.

Why is 755 so common?
755 gives the owner read, write and execute, and everyone else read and execute. That is the usual setting for directories and shared programs.

What is 644 used for?
644 gives the owner read and write while group and others can only read. It is the usual permission for ordinary files.

Do the three controls stay in sync?
Yes. Typing an octal value updates the symbolic form and the checkboxes, and editing either the symbolic text or a checkbox updates the octal value, so all three views always agree.

Are special bits supported?
A four-digit value uses the leading digit for setuid (4), setgid (2) and the sticky bit (1), which are shown as s, s and t in the symbolic form.

Is this safe to run on a server?
The tool only computes the text you would type; it never connects to a machine, so you can plan a chmod command and copy it with confidence.

Related: adjust casing with the text case converter, order output with the line sorter, format structured data with the JSON formatter, decode entities with the HTML entity decoder, and browse every browser-only tool on the all tools page.

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