What's the difference between `s` and `S` in symbolic mode?

Lowercase `s` means setuid/setgid is set AND the execute bit is set. Uppercase `S` means the special bit is set but execute is NOT — usually a configuration mistake worth investigating.

What does the sticky bit do?

On directories, the sticky bit (`1xxx`, shown as `t`) restricts file deletion: only the file's owner (or root) can delete files in that directory, even if others have write permission. Classic example: `/tmp` is `1777`.

How is umask computed?

umask is the inverse of the permissions you want new files to have. If you want files to default to `644`, umask is `022` (777 ^ 644 = 133 — but we show the standard 3-digit form by stripping leading zeros).

Chmod Calculator

A two-way calculator for Unix/Linux file permissions. Type an octal like `755` or `4755`, toggle the checkbox grid for owner/group/others read/write/execute, and see the symbolic form (`rwxr-xr-x`) update live. Special bits — setuid (4xxx), setgid (2xxx), and sticky (1xxx) — render as `s`/`S` and `t`/`T` correctly depending on whether the execute bit is also set. The output panel includes ready-to-paste `chmod` and `find -perm` commands plus the equivalent umask value, so you can copy whatever your shell session needs.

—

OctalSymbolic (ls -l)

rwxr-xr-x

Common presets

	Read (r)	Write (w)	Execute (x)
Owner (u)	r	w	x
Group (g)	r	w	x
Others (o)	r	w	x

Special bits

Setuid (4)Setgid (2)Sticky (1)

chmod command

chmod 755 file

find command

find . -type f -perm 755

Equivalent umask: 022

Note: macOS and Linux may behave differently for setgid on directories — test on your target OS.

How to use

Enter an octal (e.g. `755`, `644`, `4755`) or click a preset chip.
Use the rwx checkbox grid to toggle individual bits. The octal and symbolic forms update together.
Copy the chmod or find command from the output panel.

Frequently asked questions

What's the difference between `s` and `S` in symbolic mode?: Lowercase `s` means setuid/setgid is set AND the execute bit is set. Uppercase `S` means the special bit is set but execute is NOT — usually a configuration mistake worth investigating.
What does the sticky bit do?: On directories, the sticky bit (`1xxx`, shown as `t`) restricts file deletion: only the file's owner (or root) can delete files in that directory, even if others have write permission. Classic example: `/tmp` is `1777`.
How is umask computed?: umask is the inverse of the permissions you want new files to have. If you want files to default to `644`, umask is `022` (777 ^ 644 = 133 — but we show the standard 3-digit form by stripping leading zeros).

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