Chmod Calculator
Developer
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.
| Read (r) | Write (w) | Execute (x) | |
|---|---|---|---|
| Owner (u) | |||
| Group (g) | |||
| Others (o) |
chmod 755 file
find . -type f -perm 755
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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