Octal to Binary
Convert octal to binary — each octal digit expands to exactly 3 bits.
How to use Octal to Binary
- Enter the octal value — e.g. 755. Only digits 0–7 are valid.
- Read the binary expansion instantly: 755 → 111101101 — for permissions, read it in groups of three.
- Watch the error line: an 8 or 9 in the input is flagged by token, since those digits don't exist in base 8.
- Click “Copy result” to use the bit pattern in your work.
What is Octal to Binary?
An octal to binary converter expands a base-8 number into base 2. Like hex, octal aligns perfectly with binary — 8 is 2³, so each octal digit is exactly three bits: 7 is 111, 5 is 101, 0 is 000. Octal 755 expands to 111 101 101.
That example is no accident: 755 is the classic Unix file permission, and its binary expansion is literally the permission bits — rwx r-x r-x (owner reads, writes, executes; group and others read and execute). Octal survives in modern computing almost entirely because of this three-bits-per-digit mapping onto permission triplets.
About the Octal to Binary
Type an octal value and its binary expansion appears instantly; space-separated values convert independently.
The killer use is decoding Unix/Linux permissions: chmod 644 → 110 100 100 (rw- r-- r--), chmod 777 → 111 111 111 (everything for everyone — usually a mistake). It equally serves digital-logic homework and retrocomputing, where octal was standard on machines like the PDP-8 whose word sizes divided neatly by three.
Digits 8 and 9 don't exist in octal — the tool flags them with the exact invalid token instead of guessing. Conversion is exact at any length and runs in your browser. Binary to Octal reverses the direction.