How it works
Octal counts in base 8, hexadecimal counts in base 16. Converting means rewriting the same quantity with a different set of digits — the value never changes, only how it is written.
- Convert each octal digit to its decimal value and add them up.
- Divide that total by 16, keeping the remainders.
- Read the remainders bottom to top for the hexadecimal result.
The reverse conversion is Hexadecimal to Octal, which also handles every other base pair.
Examples
Worked examples, digit by digit:
- 12 (octal) = 10 in decimal = A (hexadecimal)
- 25 (octal) = 21 in decimal = 15 (hexadecimal)
- 377 (octal) = 255 in decimal = FF (hexadecimal)
| 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 |
Octal to Hexadecimal: frequently asked questions
- How do I convert octal to hexadecimal?
- Convert the octal number to binary first, then regroup the bits for hexadecimal. For example, octal 55 is 2D in hexadecimal. The converter above does this instantly for any value.
- What is 377 in hexadecimal?
- Octal 377 equals FF in hexadecimal (the value 255, the largest number that fits in one byte).
- Why are octal and hexadecimal used?
- Octal (base 8) is a compact way to write groups of three bits and is still used for Unix file permissions such as 755. Hexadecimal (base 16) writes each byte as two characters.