Chmod calculator for Linux and Unix file permissions
This chmod calculator converts Unix file permissions between the three ways you meet them: a grid of read, write and execute checkboxes, an octal number such as 755 or 4755, and the symbolic string such as rwxr-xr-x that ls -l prints. Change any one and the other two update instantly, along with a ready-to-paste chmod command in both numeric and symbolic form.
It is handy when a web server returns “403 Forbidden”, an SSH key is rejected as “too open”, a deploy script will not run, or you simply need to decode a line of ls -l output. The calculator also explains, in plain words, what the owner, the group and everyone else can do — and warns you about risky settings such as world-writable files or 777.
How to use the Chmod Calculator
- Tick the read, write and execute boxes for the owner, the group and others — or type an octal mode like
644or a symbolic string likerw-r--r--. - Add special bits (setuid, setgid, sticky) in the “Special” row if you need them; the octal mode gains a fourth digit.
- Choose whether the mode applies to a file or a directory to see what each permission actually allows.
- Type the file or folder name, tick “Recursive (-R)” if needed, and copy the numeric or symbolic command.
- Optionally type a change such as
u+xorgo-wand press “Apply” to see its effect on the current mode.
Chmod Calculator features
Three views, always in sync
Checkboxes, octal and symbolic notation update together, including the uppercase S and T forms for special bits without execute.
Copy-ready commands
Get chmod 755 file and the equivalent chmod u=rwx,g=rx,o=rx file, with names containing spaces quoted safely.
File vs directory meanings
Read, write and execute mean different things on folders; the explanation switches to match.
Symbolic changes
Test relative changes like a+r, g+s, o-rwx or +X exactly as chmod applies them.
Safety warnings
Flags 777, world-writable modes, setuid programs and folders missing execute permission.
How chmod numbers work
Each permission has a value: read = 4, write = 2, execute = 1. Add the values you want for one class of user to get a single digit from 0 to 7, then write three digits in the order owner, group, others. For 755: the owner gets 4 + 2 + 1 = 7 (rwx), the group gets 4 + 1 = 5 (r-x), and others also get 5 (r-x). For 640: owner 6 (rw-), group 4 (r--), others 0 (---).
An optional fourth digit at the front holds the special bits: 4 = setuid, 2 = setgid, 1 = sticky. So 4755 is 755 plus setuid, and 1777 is 777 plus the sticky bit, the mode of /tmp.
| Mode | Symbolic | Typical use |
|---|---|---|
| 644 | rw-r--r-- | Web pages, images, config files |
| 755 | rwxr-xr-x | Folders, scripts and programs |
| 600 | rw------- | SSH private keys, .env files, secrets |
| 700 | rwx------ | Private folders such as ~/.ssh |
| 664 / 775 | rw-rw-r-- / rwxrwxr-x | Files and folders shared with a team group |
| 2775 | rwxrwsr-x | Shared project folder that keeps its group |
| 1777 | rwxrwxrwt | Shared temporary folder like /tmp |
Permissions on directories
- Read (r) lets you list the names inside the folder.
- Write (w) lets you create, rename and delete entries — but only together with execute.
- Execute (x) lets you enter the folder and reach files inside it by name. Without x on every parent folder, a file cannot be opened even if its own mode allows it — a frequent cause of web-server 403 errors.
- setgid on a folder makes new files inherit the folder’s group, which keeps shared project folders consistent. On Linux, a plain numeric mode such as
chmod 755does not clear it; usechmod g-s. - Sticky bit on a folder means only a file’s owner (or root) may delete or rename it, even though everyone can write to the folder.
Safe permission habits
Start from the least access that works. Web content usually needs 644 for files and 755 for folders; secrets such as SSH keys need 600, and OpenSSH refuses private keys that others can read. When several people need write access, put them in a shared group and use 664/775 rather than 777. New files get their starting mode from your umask: with the common umask 022, files are created as 644 and folders as 755, while 002 gives 664 and 775. If you manage permissions from a script, the number base converter helps when you need the decimal or binary value of a mode.
Chmod Calculator FAQ
What does chmod 755 mean?
The owner can read, write and execute (7), while the group and everyone else can read and execute (5). It is the standard mode for folders, scripts and programs that others should be able to run but not modify. In symbolic form it is rwxr-xr-x.
What does chmod 644 mean?
The owner can read and write (6), and the group and others can only read (4): rw-r--r--. It is the usual mode for ordinary files such as HTML pages, images and configuration files.
Is chmod 777 safe?
Rarely. 777 lets every user on the system modify, replace or delete the file, which on a server can let a compromised process plant code. Fix permission errors by changing the owner (chown) or group instead, and use 755/775 for folders.
How do I make a file executable?
Run chmod +x file to add execute for everyone, or chmod u+x file for the owner only. In this chmod calculator, tick the Execute boxes or type the change into “Apply a symbolic change”.
What do s, S, t and T mean in ls -l output?
A lowercase s in the owner or group execute position means setuid or setgid is set together with execute; an uppercase S means the special bit is set but execute is not. A t in the last position is the sticky bit with execute for others, and T is the sticky bit without it.
How do I set 644 on files and 755 on folders recursively?
chmod -R applies one mode to everything, which would make every file executable. Use find instead: find dir -type d -exec chmod 755 {} + for folders and find dir -type f -exec chmod 644 {} + for files.