About chmod Calculator — Octal & Symbolic Permissions
Unix file permissions can be written two ways: symbolic (rwxr-xr-x) and octal (755). The symbolic form spells out read, write, and execute for the owner, the group, and everyone else; the octal form packs the same nine bits into three digits. Translating between them in your head is easy to get wrong, especially once the setuid, setgid, and sticky bits enter the picture.
This free chmod calculator converts octal permissions to symbolic and back, and gives you an interactive rwx grid you can click to build a mode visually. Toggle a checkbox and the octal and symbolic fields update instantly; type a value and the grid follows. It handles the special bits and runs entirely in your browser — nothing you enter is uploaded.
Features
- Interactive owner/group/other × read/write/execute grid, synced live
- Convert octal (755) to symbolic (rwxr-xr-x) and back
- Full support for the setuid, setgid, and sticky special bits
- Copy either form with one click; works completely offline
How to use
- Click the rwx checkboxes to set read, write, and execute for owner, group, and other.
- Or type directly into the octal or symbolic field — the grid and the other field follow.
- Toggle setuid, setgid, or sticky if you need a special bit.
- Copy the octal value to paste into a chmod command.
Frequently asked questions
What does chmod 755 mean?
Mode 755 is rwxr-xr-x: the owner can read, write, and execute; the group and everyone else can read and execute but not write. It is the common setting for directories and executable scripts.
What is the difference between 644 and 755?
644 (rw-r--r--) grants no execute permission, which suits regular files like documents and config. 755 (rwxr-xr-x) adds execute for everyone, which is what directories and runnable programs need.
What are the setuid, setgid, and sticky bits?
They are a fourth, leading octal digit. setuid (4) runs a program as its owner, setgid (2) runs it as its group or makes new files in a directory inherit the group, and the sticky bit (1) on a shared directory like /tmp stops users deleting each other’s files.
Why is the execute letter sometimes s, S, t, or T?
A special bit reuses the execute slot. Lower-case (s or t) means the special bit is set and execute is also on; upper-case (S or T) means the special bit is set but execute is off.
Is anything I type sent to a server?
No. All conversion happens locally in your browser with plain arithmetic. Your input never leaves your device.
Related tools
Everything runs locally in your browser — your input is never uploaded.