Convert octal to binary
17 in octal is 1111 in binary. Each digit is multiplied by its place value — the base raised to the digit's position, counting from zero on the right — and the products are added. The page prints every one of those products rather than only the total. The conversion is exact: bases are positional notation for the same number, so nothing is rounded and the result can be checked digit by digit.
Conversion rules checked · How we check
17 in octal
1111
How it gets there
- Each digit carries its place
- 1 × 8¹ + 7 × 8⁰
- Which is
- 8 + 7 = 15
- Divide by 2, keeping the remainders
- 15 ÷ 2 = 7 remainder 1 7 ÷ 2 = 3 remainder 1 3 ÷ 2 = 1 remainder 1 1 ÷ 2 = 0 remainder 1
- Read the remainders upwards
- The last remainder is the leading digit.
octal to binary, at a glance
One octal digit is exactly three binary digits, so this conversion is done by grouping rather than by dividing: split the binary into threes from the right and read each group. It is why Unix file permissions are written in octal — three bits, read-write-execute, per group.
| octal | binary |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 10 |
| 3 | 11 |
| 4 | 100 |
| 5 | 101 |
| 6 | 110 |
| 7 | 111 |
| 10 | 1000 |
| 11 | 1001 |
| 12 | 1010 |
| 13 | 1011 |
| 14 | 1100 |
| 15 | 1101 |
| 16 | 1110 |
| 17 | 1111 |
| 20 | 10000 |
Why is the working shown?
Every other converter of this kind prints the answer and stops. A base is a positional system, so the answer is a sum you can check: each digit is multiplied by the base raised to its position, and the results are added. Going the other way is repeated division, reading the remainders upwards. Neither is a black box, and this page refuses to be one.