Chmod Permissions Calculator — Free
Runs 100% in your browser — your files never leave your device.
Unix permission numbers are easy to transpose when owner, group, and public access differ. Toggle read, write, and execute for each group or type a three-digit octal mode, then copy the matching chmod command and symbolic rwx representation.
How it works
- 1
Enter octal or toggle permissions
- 2
Review symbolic and numeric modes
- 3
Copy the chmod command
About this tool
How the three digits work
Each digit covers one audience — owner, group, others — and sums three permissions: read is 4, write is 2, execute is 1. 7 means all three (4+2+1), 6 means read and write, 5 means read and execute. The calculator builds the octal from the checkboxes you toggle, and shows what each digit means as you go.
The conventions worth knowing
755 for directories and executables (owner writes, everyone reads and executes), 644 for regular files (owner writes, everyone reads), 600 for private files like keys (owner only), 700 for private directories. Most servers refuse permissive key files — 600 is not optional for SSH keys.
Security comes from the last digit
The "others" digit is what the world gets. World-writable files (an others digit containing 2) are how accidental exposures happen — every permission audit starts by looking for them. Set the smallest others-permission that still works, then verify with a listing.
Frequently asked questions
What is the difference between 644 and 600?
644 lets everyone read the file; 600 restricts it to the owner. Config files with secrets, SSH keys, and anything personal belong at 600.
Why do directories need the execute bit?
Execute on a directory means "enter and traverse" — without it, the directory cannot be accessed even if its files are readable. That is why directories conventionally get 755 rather than 644.
How do I apply the result?
Copy the octal into chmod: chmod 755 filename, or chmod -R 755 directory for recursion. Recursion applies to everything inside — check what you are aiming at first.