Chmod Calculator
Tick read, write and execute for owner, group and other to get the octal (like 755) and symbolic (rwxr-xr-x) Unix permissions — plus the ready-to-copy command.
| Read (4) | Write (2) | Execute (1) |
|---|
chmod 755 filenameUnix file permissions use three octal digits — one for the owner, one for the group and one for others — where each digit adds read (4), write (2) and execute (1). So 755 means the owner has all three (7) and the group and others have read and execute (5), written symbolically as rwxr-xr-x. Tick the boxes to build a permission, or type an octal number to see the boxes and symbolic string update. A common rule is 644 for files and 755 for directories and scripts.
Frequently Asked Questions
What does chmod 755 mean?
chmod 755 sets permissions with three octal digits — owner, group, other — each the sum of read (4), write (2) and execute (1). So 7 is read+write+execute and 5 is read+execute. 755 means the owner can read, write and execute, while the group and others can read and execute but not write — symbolically rwxr-xr-x. It is a common setting for directories and executable scripts.
How do the octal permission numbers work?
Each class — owner, group, other — gets one octal digit from 0 to 7, formed by adding the permissions you want: read is 4, write is 2, execute is 1. Read+write is 6, read+execute is 5, all three is 7. You write the three digits in order: owner, group, other. Read-write for the owner and read-only for everyone else is 644.
What is the difference between 644 and 755?
644 (rw-r--r--) gives the owner read and write and everyone else read only, with no execute — the usual permission for regular files. 755 (rwxr-xr-x) adds the execute bit for all three classes, needed for directories (to enter them) and for scripts and programs (to run them). Rule of thumb: 644 for files, 755 for directories and executables.
Does this run in my browser?
Yes. The chmod calculator is pure arithmetic that runs entirely in your browser — nothing is uploaded or stored, no sign-up, and it works offline once loaded. Tick the read/write/execute boxes to build a permission, or type an octal number like 755 and watch the boxes and the symbolic string update, plus the ready-to-copy chmod command.