Convert Unix file permissions between octal and symbolic form.
Calculated locally in your browser.
How do you convert chmod permissions between octal and symbolic?
Each group uses read = 4, write = 2 and execute = 1; add the values per group for the octal digit, so 7 = rwx, 5 = r-x, 4 = r--. Three groups (owner, group, others) give the three-digit number. For example, 755 means rwxr-xr-x: the owner can read, write and execute, while group and others read and execute.
Understanding your result
Permissions apply to three classes — owner, group and others — each with read, write and execute bits. Common values include 644 (rw-r--r--) for files and 755 (rwxr-xr-x) for directories and scripts. Avoid 777, which lets anyone modify a file. The leading bit for setuid, setgid and sticky is not covered here.
Formula and method
Each group has read = 4, write = 2 and execute = 1. Add the values per group for the octal digit: 7 = rwx, 5 = r-x, 4 = r--. Three groups give the three-digit octal.
Worked example
755 means rwxr-xr-x: the owner can read, write and execute (7), while group and others can read and execute (5).
How to use this tool
- Choose octal or symbolic input.
- Enter the permission, such as 755 or rwxr-xr-x.
- Read the converted form and the breakdown.
Common mistakes to avoid
- Using 777 on web files, which is insecure.
- Mixing up the order — it is owner, then group, then others.
- Forgetting directories usually need the execute bit to be entered.
About the Chmod Calculator
The Chmod Calculator converts Unix file permissions between octal numbers like 755 and symbolic notation like rwxr-xr-x. It shows exactly what owner, group and others can do, plus the chmod command to use.
Who should use this tool
Developers, sysadmins and anyone working on Linux, macOS or web servers.
Benefits
- Octal to symbolic and back.
- Per-group breakdown of read, write and execute.
- Ready-to-copy chmod command.
- Private — calculated entirely in your browser.
Practical use cases
- Setting the right permissions on a web file or folder.
- Decoding a permission string from ls -l.
- Learning how Unix permissions work.
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Frequently asked questions
What does chmod 755 mean?
It sets rwxr-xr-x: the owner can read, write and execute, while group and others can read and execute. It is common for directories and scripts.
What is the difference between 644 and 755?
644 (rw-r--r--) suits regular files, allowing the owner to edit and everyone to read. 755 adds execute permission, which directories and programs need.
Is 777 safe?
Usually not. 777 lets anyone read, write and execute the file, which is a security risk on shared or web servers. Use the least permission needed.