What is the Decimal to Octal Converter?
This tool converts decimal numbers (base-10) to octal numbers (base-8), a format commonly used in Unix and Linux systems.
Why Convert Decimal to Octal?
File Permissions
Programming
Understanding Binary
Legacy Compatibility
The Conversion Method
Divide by 8 repeatedly and record each remainder, then read the remainders from bottom to top.
How to Use
Enter the Decimal Number
Type any positive integer using the digits 0–9.
View the Octal Result
The result uses only the digits 0–7 and updates instantly.
Apply the Value
Copy the result to use with chmod or in your code.
Permission Calculation
For Unix permissions, each octal digit represents owner, group, and others, where 4 = read, 2 = write, 1 = execute.
| Value | Permission |
|---|---|
| 4 | read (r) |
| 2 | write (w) |
| 1 | execute (x) |
| 7 | 4 + 2 + 1 = rwx (full access) |
Frequently Asked Questions
Why does the result never contain 8 or 9?
Octal is base-8, so it only uses the digits 0 through 7. The values 8 and 9 do not exist in this system.
Why is 493 equal to 755 in octal?
755 in octal is 7×64 + 5×8 + 5×1 = 448 + 40 + 5 = 493. That is why chmod 755 corresponds to the decimal value 493.
How does this help with chmod?
If you know a permission as a decimal value, convert it to octal to get the three-digit chmod code for owner, group, and others.
How do I convert octal back to decimal?
Type an octal number directly into the result field, or press the swap button to reverse the conversion direction.
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