Chmod Calculator
Build Unix file permissions visually.
How to use
- 1 Tick read, write and execute for the owner.
- 2 Repeat for the group and for others.
- 3 Read off the octal mode and symbolic string.
- 4 Copy the generated chmod command.
About Chmod Calculator
The Chmod Calculator turns confusing Unix file permissions into a simple set of checkboxes.
Tick read, write and execute for the owner, the group and others, and the tool instantly shows you the three-digit octal mode (like 755), the symbolic string (like rwxr-xr-x) and a copy-ready command such as “chmod 755 file”.
Permissions on Linux and macOS combine three numbers — read is 4, write is 2 and execute is 1 — added together for each of the three identity classes.
Remembering that 6 means read plus write, or that 644 maps to rw-r--r--, is exactly the kind of thing this calculator does for you so you do not have to.
The symbolic and octal views stay in sync as you toggle, which makes it easy to learn the mapping while you work.
It is ideal when hardening a server, fixing “permission denied” errors, writing a deploy script, or teaching how Unix permissions work.
The calculator is entirely client-side: nothing you select is sent anywhere, and it keeps working offline once the page has loaded.
FAQ
How do the octal numbers map to permissions?
Read is 4, write is 2 and execute is 1. Add them per class: read+write+execute is 7, read+execute is 5, read+write is 6, and read only is 4.
What is the difference between 755 and 644?
755 (rwxr-xr-x) is typical for executables and directories; the owner can do everything, others can read and run. 644 (rw-r--r--) suits regular files: owner reads and writes, others only read.