This free online binary to octal converter instantly translates any binary (base-2) number into its octal (base-8) equivalent. Enter a binary value below to see the converted result right away.
Octal is base 8, and 8 is 2 cubed, so one octal digit corresponds to exactly three bits. Working from the rightmost bit, cut the binary number into groups of three, add zeros to the left of the last group if it is short, and write each group as a single digit from 0 to 7.
Internally, the converter parses the input as a base-2 value and prints that value in base 8. The answer is identical to the grouping method, and the output never contains an 8 or a 9.
Eight bits split from the right as 11 010 111. Padding the left group gives 011, 010 and 111, which are 3, 2 and 7. So 11010111 in binary is 327 in octal. Checking through decimal: binary 11010111 is 215, and octal 327 is 3 × 64 + 2 × 8 + 7 = 215.
| Bits | 000 | 001 | 010 | 011 | 100 | 101 | 110 | 111 |
|---|---|---|---|---|---|---|---|---|
| Octal | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 |
Within a group the bits are worth 4, 2 and 1, so 101 is 4 + 1 = 5 and 110 is 4 + 2 = 6. Once that is familiar, most conversions can be done at a glance.
The best-known everyday use of octal is in Linux and Unix file permissions. Each file has three sets of read, write and execute flags, for the owner, the group and everyone else. Each set is three bits, so each becomes one octal digit for commands such as chmod.
| Permissions | Binary | Octal | Typical use |
|---|---|---|---|
| rwxr-xr-x | 111 101 101 | 755 | Programs, scripts and directories |
| rw-r--r-- | 110 100 100 | 644 | Ordinary files such as web pages |
| rwx------ | 111 000 000 | 700 | Private folders only the owner can open |
Enter 111101101 into the converter and it returns 755, the same digits you would type after chmod.