Symbolic vs numeric — which should I use?

Numeric (755, 644) is unambiguous and the common form in scripts. Symbolic (u+x, g-w) is safer for incremental changes — avoids accidentally clearing other bits.

What do 755, 644, 600 mean?

755: owner all, group+others read+execute (typical for directories and executables). 644: owner rw, others r (typical for data files). 600: owner rw, others nothing (private keys).

Does it show the effect visually?

Yes — an rwxrwxrwx grid lights up showing which bits are set. Much faster to verify than mentally decoding 3 octal digits.

What about setuid and sticky bits?

The 4-digit form (4755, 1777) covers these. Setuid (4), setgid (2), sticky (1). The tool handles both 3-digit and 4-digit input.

Chmod Calculator | DevTools Surf

DevTools Surf

Example: Chmod Calculator

A worked example, rendered from real sample data. Sign in to run the tool on your own input.

Input

Output

Octal:     755  (0755 with special bits)
Symbolic:  rwxr-xr-x
Command:   chmod 755 path/to/file
Clauses:   chmod u=rwx,g=rx,o=rx path/to/file

Who can do what:
  Owner   rwx  (7)  read, write, execute
  Group   r-x  (5)  read, execute
  Others  r-x  (5)  read, execute

Reference:
  644  rw-r--r--  regular file
  755  rwxr-xr-x  script or directory
  600  rw-------  private key or secret
  700  rwx------  private directory
  1777 rwxrwxrwt  shared temp directory

About Chmod Calculator

Chmod Calculator preview - Generators tool

Convert between symbolic and numeric Unix file permissions. Part of the DevTools Surf developer suite. Browse more tools in the Generators collection.

Use Cases

Calculating deployment script permissions for CI/CD pipelines
Setting correct permissions for SSH key files (600 or 400)
Converting symbolic permissions from ls -la output to numeric
Configuring web server file permissions for uploads directories

Tips

Toggle permission checkboxes to see the numeric value update
Convert between symbolic notation like rwxr-xr-x and 755
Verify directory permissions separately from file permissions

Fun Facts

Unix file permissions were designed by Ken Thompson and Dennis Ritchie for the first version of Unix at Bell Labs in 1971.
The sticky bit (1000) was originally used to keep programs in swap space for faster loading; today it prevents file deletion in shared directories.
The SUID bit (4000) allows a program to run with the permissions of the file owner, which is how the passwd command can modify /etc/shadow.

FAQ

Symbolic vs numeric — which should I use?: Numeric (755, 644) is unambiguous and the common form in scripts. Symbolic (u+x, g-w) is safer for incremental changes — avoids accidentally clearing other bits.
What do 755, 644, 600 mean?: 755: owner all, group+others read+execute (typical for directories and executables). 644: owner rw, others r (typical for data files). 600: owner rw, others nothing (private keys).
Does it show the effect visually?: Yes — an rwxrwxrwx grid lights up showing which bits are set. Much faster to verify than mentally decoding 3 octal digits.
What about setuid and sticky bits?: The 4-digit form (4755, 1777) covers these. Setuid (4), setgid (2), sticky (1). The tool handles both 3-digit and 4-digit input.

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