How it works
Binary counts in base 2, octal counts in base 8. Converting means rewriting the same quantity with a different set of digits — the value never changes, only how it is written.
- Convert each binary digit to its decimal value and add them up.
- Divide that total by 8, keeping the remainders.
- Read the remainders bottom to top for the octal result.
Shortcut: group the binary digits in threes from the right; each group is one octal digit.
The reverse conversion is Octal to Binary, which also handles every other base pair.
Examples
Worked examples, digit by digit:
- 1010 (binary) = 10 in decimal = 12 (octal)
- 10101 (binary) = 21 in decimal = 25 (octal)
- 11111111 (binary) = 255 in decimal = 377 (octal)
| Decimal | Binary | Octal | Hexadecimal |
|---|---|---|---|
| 0 | 0 | 0 | 0 |
| 1 | 1 | 1 | 1 |
| 2 | 10 | 2 | 2 |
| 4 | 100 | 4 | 4 |
| 8 | 1000 | 10 | 8 |
| 10 | 1010 | 12 | A |
| 15 | 1111 | 17 | F |
| 16 | 10000 | 20 | 10 |
| 32 | 100000 | 40 | 20 |
| 64 | 1000000 | 100 | 40 |
| 100 | 1100100 | 144 | 64 |
| 255 | 11111111 | 377 | FF |
Binary to Octal: frequently asked questions
- How do I convert binary to octal?
- Group the binary digits in threes from the right and convert each group to one octal digit. For example, binary 101101 is 55 in octal. The converter above does this instantly for any value.
- What is 11111111 in octal?
- Binary 11111111 equals 377 in octal (the value 255, the largest number that fits in one byte).
- Why are binary and octal used?
- Binary (base 2) is how computers store data, as bits that are either 0 or 1. Octal (base 8) groups bits in threes.