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: 4 is setuid, 2 is setgid and 1 is the sticky bit, so 0755 is the same as 755. This calculator handles only the three permission digits. If you type 4755 it keeps 755 and drops the setuid bit, so use the chmod symbolic converter for modes with special bits.

What permissions should an SSH key have?

Set a private key to 600 (rw-------) or 400 (r--------) and the ~/.ssh folder to 700. OpenSSH refuses a private key that group or others can read and warns that its permissions are too open. Public keys (.pub) can stay at 644.

What does chmod 777 do, and should I use it?

777 (rwxrwxrwx) lets every user on the system read, change and run the file. On a web server that means any process or hacked account can rewrite it. Use 755 for folders and 644 for files, and give write access through the owner or group instead.

Chmod Calculator

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.

Each digit of a chmod number adds read (4), write (2) and execute (1), for owner, group and others in that order.

Permission Checkboxes

	Read	Write	Execute

Or type a numeric value

Result

Numeric

000

Symbolic

----------

Command

chmod 000 filename

Quick answer

Each digit of a chmod number adds read (4), write (2) and execute (1), for owner, group and others in that order. So 755 is rwxr-xr-x: the owner can read, write and run the file, everyone else can read and run it. 644 (rw-r--r--) is the usual mode for web files. Tick the boxes or type a number to see both forms.

Examples

Mode	Symbolic	Typical use
755	rwxr-xr-x	Scripts, folders
644	rw-r--r--	Web pages, configs
600	rw-------	SSH private keys
700	rwx------	The ~/.ssh folder
664	rw-rw-r--	Files a team edits
777	rwxrwxrwx	Anyone can change it

Tick the boxes or type a number like 755.

Summary

This calculator converts between the three common ways Unix and Linux systems express file permissions: checkboxes, a three-digit octal number like 755, and a symbolic string like rwxr-xr-x. Toggle any read, write, or execute checkbox for owner, group, or other and the numeric value and symbolic string update instantly. Type a numeric value directly and the matching checkboxes and symbolic string update to match, which is useful when you already know the target mode from a script or a server configuration file.

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: 2026-09-09 · Reviewed by Nham Vu