Convert decimal to octal (base 10 → base 8)
Use this converter when you have decimal integers (base 10) and need their octal representation (base 8).
This page is a focused Decimal → Octal variant built for speed: batch mode is enabled by default (one value per line).
Need other bases (binary/hex), prefixes, or extra formatting? Open the full Number Base Converter.
How to use it
- Paste your decimal values into the input (left).
- Use one number per line.
- Copy the octal results from the output (right).
Signed values are supported:
-9becomes-11+64becomes100
Input rules (decimal)
Integers only
Valid examples:
08+42-42000123(leading zeros are fine)
Not supported:
3.141e612,345(remove commas)
Whitespace is okay
Extra spaces and empty lines are fine. In batch mode, each line is converted independently.
Output format (octal)
- Output uses digits
0–7 - Negative values keep a leading
- - No
0oprefix by default
Examples:
8→109→1164→100255→377-42→-52
Batch example (one per line)
Input (decimal):
10
64
255
-42
3.14Output (octal):
12
100
377
-52
!ERROR: Decimal input may contain only digits 0–9One invalid line won’t break the rest.
Common use cases
File permissions (chmod-style thinking)
Octal is widely used to represent Unix permission bits (e.g. 755, 644).
If you’re translating a bitmask or permission value you saw in decimal into a more familiar octal form, this converter is handy.
Embedded systems and bit fields
Octal groups bits in chunks of 3, which can be a convenient way to inspect large binary values.
Learning number bases
Octal is a great bridge between binary and decimal, especially when you want a compact representation without jumping to hex.
Troubleshooting
“Invalid digit for decimal”
Decimal input can contain only digits 0–9 and an optional leading + or -.
Remove commas, periods, and scientific notation.
Notes
- This is number base conversion for integers, not text/byte encoding.
- Everything runs locally in your browser — nothing is uploaded.
