Chmod Calculator
Permissions
| Read (r) | Write (w) | Execute (x) | |
|---|---|---|---|
| Owner | |||
| Group | |||
| Others |
Special Permissions
Quick Presets
Result
chmod 644 filename
Free Chmod Calculator
Calculate Linux/Unix file permissions with an interactive checkbox grid. Convert between numeric (octal) and symbolic notation. Get the chmod command ready to copy and an explanation of what each permission means.
What Is chmod?
chmod (change mode) is a Unix/Linux command that sets file permissions. Permissions control who can read, write, or execute a file. There are three permission groups: Owner (user), Group, and Others (world).
Permission Values
- Read (r = 4) — View file contents or list directory
- Write (w = 2) — Modify file or add/remove files in directory
- Execute (x = 1) — Run file as program or access directory
Each group's permissions are the sum of its values. For example, rwx = 4+2+1 = 7, rw- = 4+2+0 = 6, r-- = 4+0+0 = 4.
Common Permission Settings
644— Default for files (owner: rw, group & others: read only)755— Default for directories and scripts (owner: rwx, group & others: rx)600— Private files (owner: rw, nobody else)700— Private directories (owner: rwx, nobody else)444— Read-only for everyone777— Full access for everyone (⚠️ security risk)
Frequently Asked Questions
What are special permissions?
SUID (4) — File executes as the file owner. SGID (2) — File executes as the group owner; for directories, new files inherit the group. Sticky Bit (1) — Only the file owner can delete files in the directory (commonly used on /tmp).
What does the leading zero mean in 0755?
The leading digit represents special permissions (SUID, SGID, Sticky Bit). 0755 means no special permissions. 4755 would set SUID + rwxr-xr-x.