CALCULATORS
Unix Permissions Calculator
Convert chmod octal values into readable owner, group, and public permissions.
CHMOD MODE
Read a permission value
Example: 755 = owner can read/write/execute; everyone else can read/execute.
Unix permissions calculator guide
Translate Unix chmod values into readable owner, group, and others permissions.
The calculator explains a mode; it never changes permissions on your machine or server.
Reading the three octal digits
The first digit describes the owner, the second the group, and the third everyone else. Within each digit, read is 4, write is 2, and execute is 1; add the values to combine permissions.
Common examples
- 644: owner can read/write; group and others can read.
- 755: owner can read/write/execute; group and others can read/execute.
- 600: owner can read/write; group and others have no access.
Use least privilege
Choose the narrowest permissions that let a file or process work. Broad write or execute permissions can expose data or increase risk, especially on shared systems.
Tip: Remember that directory permissions control listing, traversal, and creation behaviour differently from regular files.
Frequently asked questions
What does chmod 755 mean?
The owner can read, write, and execute; group and others can read and execute.
Does this change file permissions?
No. It only calculates and explains the value; you must apply permissions separately on your system.
Are Unix permissions the whole security model?
No. Ownership, ACLs, umask, filesystem features, process identity, and application controls can also affect access.
Privacy note: permission calculations happen in your browser. Nothing is uploaded.