What does chmod 755 mean?

755 grants the owner read, write, and execute; group and everyone else get read and execute only. It is the common mode for executable scripts and directories.

What does chmod 644 mean?

644 grants the owner read and write; group and everyone else get read-only. It is the common mode for regular files like HTML, CSS, or config files that should not be executable.

How is the numeric value calculated?

Each permission has a weight: read = 4, write = 2, execute = 1. Add the weights for owner, group, and other separately to get each of the three digits, for example rwx = 4+2+1 = 7.

What is the difference between numeric and symbolic chmod?

Numeric mode uses three digits like 755, one per owner/group/other. Symbolic mode uses letters like rwxr-xr-x, where each triplet of r, w, x (or a dash for no permission) represents the same information in a more readable form.

Does this tool run chmod on my files?

No. This is a calculator only, it runs entirely in your browser and does not touch any server or file. Copy the generated command and run it yourself in a terminal.

What does the leading digit before three digits, like 0755, mean?

A fourth leading digit sets special bits: setuid, setgid, and the sticky bit. This calculator focuses on the standard three-digit owner/group/other permissions, which cover the vast majority of everyday chmod use.

Chmod Calculator

Name: Chmod Calculator
Availability: InStock
Author: Nham Vu

Toggle owner/group/other read, write, execute checkboxes to get the chmod number and symbolic string, or type a number to see the boxes checked.

Permission Checkboxes

	Read	Write	Execute

Or type a numeric value

Result

Numeric

000

Symbolic

----------

Command

chmod 000 filename

Summary

Toggle owner/group/other read, write, execute checkboxes to get the chmod number and symbolic string, or type a number to see the boxes checked.

How it works

Check or uncheck read, write, execute boxes for owner, group, and other.
The numeric chmod value (e.g. 755) and the symbolic string (e.g. rwxr-xr-x) update live.
Or type a numeric value like 644 directly into the number field.
The checkboxes and symbolic string update to match the number you typed.
Click "Copy chmod command" to copy a ready-to-run chmod command.

Use cases

Figure out what chmod 755 or chmod 644 actually grants before running the command.
Set correct permissions for web server files and directories.
Translate a symbolic permission string seen in `ls -l` output back into a number.
Teach or learn how Unix file permission bits map to octal digits.
Double-check a deployment script or Dockerfile RUN chmod line before shipping.
Work out permissions for a cron job or SSH key file that requires a specific mode.

Frequently Asked Questions

Last updated: 2026-07-22 · Reviewed by Nham Vu