Convert Unix file permissions between checkbox, octal (755), and symbolic (rwxr-xr-x) notation with setuid, setgid, and sticky bits.
Updated
| Who | read | write | execute |
|---|---|---|---|
| owner | |||
| group | |||
| other |
rw-r--r--chmod 644 fileQuick start
Tick permissions or type an octal value, copy the chmod command — all local.
Tick read/write/execute for owner, group, and other, or type an octal value.
Enable setuid, setgid, or sticky if you need them.
Read the octal and symbolic forms and copy the ready-to-run chmod command.
In-depth guide
Unix file permissions look cryptic — 755, rwxr-xr-x, 4755 — but they encode a simple grid: three audiences (owner, group, other) each with three rights (read, write, execute). This calculator lets you tick the boxes or type the octal value and shows the octal, symbolic, and ready-to-run chmod command, all in your browser.
Each permission has a value: read = 4, write = 2, execute = 1. Add them up per audience to get one octal digit (0–7). So rwx = 4+2+1 = 7, r-x = 4+1 = 5, rw- = 4+2 = 6. Three digits — owner, group, other — make a mode like 755 or 644.
An optional leading fourth digit holds the special bits: setuid (4), setgid (2), and the sticky bit (1).
/tmp with the sticky bit so users only delete their own files.rwxr-xr-x), and chmod <mode> file forms.setuid on a writable executable is dangerous — it lets the program run with the owner's privileges. Use it sparingly and never on scripts you do not control.
cd into a directory even if you can read it.This is a pure calculator. It computes octal and symbolic modes in your browser and prints a command for you to run — it never touches your filesystem and never sends anything over the network. Close the tab and there is nothing to clean up.
Each digit is the sum of read (4), write (2), and execute (1) for owner, group, and other. 755 = owner rwx (7), group r-x (5), other r-x (5) — the typical mode for a directory or an executable script: the owner can change it, everyone can read and run it.
644 (rw-r--r--) grants no execute bit — correct for regular files like text, images, and HTML. 755 (rwxr-xr-x) adds execute for everyone, which directories need to be entered and scripts need to be run. Applying 755 to a plain data file is harmless but unnecessary; applying 644 to a directory makes it unusable.
It holds the special bits: setuid (4), setgid (2), and sticky (1). For example 4755 runs the file with the owner's privileges (setuid), and 1777 on /tmp sets the sticky bit so users can only delete their own files. Tick the setuid/setgid/sticky boxes to set it.
A capital S or T means the special bit is set but the corresponding execute bit is not, which is usually a mistake. A lowercase s or t means both are set (the normal case). The calculator shows this faithfully so you can catch a misconfigured mode.
No. It only computes the numbers and prints the chmod command for you to run yourself. Nothing executes and nothing is uploaded — it is a pure calculator running in your browser.
Almost never. 777 grants read, write, and execute to everyone, so any user or process can modify or replace the file. It is a common but dangerous quick fix for permission errors; the right answer is usually correct ownership plus 644 or 755.
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