Chmod Calculator
Calculate Linux file permissions in numeric (octal) and symbolic notation. Toggle read, write, and execute per role, or type a chmod code to see it decoded.
Owner
You, the file's creator
Group
Everyone in the file's group
Public
Everyone else on the system
Special permissions(advanced, rarely needed)
Common presets
Every file and folder on a Linux, macOS, or Unix system carries a permission set that decides who can read it, write to it, or execute it. That permission set is what `chmod` changes — and it's usually written as a 3-digit octal code like 644 or 755.
This calculator works in both directions. Toggle the checkboxes above to build a permission set and watch the numeric and symbolic codes update instantly, or paste an existing code — numeric or symbolic — into either field to see exactly which boxes it turns on.
How to use the chmod calculator
- 1Tick Read, Write, and Execute for Owner, Group, and Public to describe who can do what.
- 2The Numeric field (e.g. 755) and Symbolic field (e.g. rwxr-xr-x) update together as you toggle.
- 3Already have a code? Type it into either field — the checkboxes and the other field sync to match.
- 4Copy the ready-made command and run it: chmod <code> filename.
Common chmod codes
| Numeric | Symbolic | Typical use |
|---|---|---|
| 644 | -rw-r--r-- | Regular files — owner edits, everyone else reads |
| 600 | -rw------- | Private files — only the owner can read or write |
| 755 | -rwxr-xr-x | Scripts and folders — owner has full control, others can read/run |
| 700 | -rwx------ | Private scripts and folders — owner only |
| 664 | -rw-rw-r-- | Files shared with a group, read-only for everyone else |
| 775 | -rwxrwxr-x | Folders shared with a group, executable |
| 777 | -rwxrwxrwx | Full access for everyone — avoid on production servers |
Frequently asked questions
What does chmod 755 mean?+
755 gives the file's owner full access (read, write, execute) while the group and everyone else get read and execute access, but not write. It's the standard permission for scripts, executables, and directories that need to be entered but not modified by other users.
What does chmod 644 mean?+
644 lets the owner read and write the file, while the group and everyone else can only read it. It's the standard default for regular files like HTML, CSS, images, and config files that shouldn't be run as programs.
What's the difference between numeric and symbolic notation?+
Numeric (octal) notation represents each permission group — owner, group, other — as a single digit from 0-7, where 4=read, 2=write, and 1=execute, added together. Symbolic notation spells the same thing out as letters, like rwxr-xr-x, which some admins find easier to read at a glance.
What are setuid, setgid, and the sticky bit?+
These are special permission bits shown as a leading 4th digit in numeric notation. Setuid (4) makes a program run with its owner's privileges rather than the user who launched it. Setgid (2) does the same for the group, and on directories it makes new files inherit the folder's group. The sticky bit (1) on a shared directory stops users from deleting files they don't own — commonly seen on /tmp.
Why isn't chmod 777 a good idea?+
777 grants read, write, and execute to literally everyone with access to the system — including other users and, on a web server, potentially the public. It's occasionally used to unblock a permissions error quickly, but it's rarely the right long-term fix and is a common source of security issues.