Binary to octal converter
Enter a binary number and get its octal value instantly, plus the other bases and the step-by-step working. Handles huge numbers, negatives and fractions.
Working for 1011012
Each octal digit is exactly 3 bits, so you can convert group by group, no arithmetic needed:
How to convert binary to octal
- Group the bits in threes from the right, padding the left group with zeros.
- Replace each group with one octal digit (000 = 0 … 111 = 7).
- 110 101 = 65 in octal.
Binary is how hardware stores everything: bit flags, network masks, file permissions and machine code are all patterns of 1s and 0s. Octal survives mainly in Unix file permissions (chmod 755), in some older systems, and in C/Python literals such as 0o755.
See place value move
Every bit is worth twice the bit to its right. Flip the switches and watch the decimal, hex and octal values rebuild.
32 + 8 + 4 + 1 = 45 · hex 2D · octal 55
Related conversions
Binary to decimal · Binary to hex · Octal to binary · Decimal to octal · Hex to octal · any base 2–36 · signed (two's complement)
Questions people ask
How do you convert binary to octal?
Group the bits in threes from the right, padding the left group with zeros. Replace each group with one octal digit (000 = 0 … 111 = 7). 110 101 = 65 in octal.
What is 101101 in octal?
101101 in binary (base 2) is 55 in octal (base 8).
Does it handle negative numbers and fractions?
Yes. A leading minus sign is kept, and digits after a point are converted too. Some fractions that end in one base repeat forever in another (0.1 in decimal is 0.000110011… in binary), so the result is cut at 24 digits and marked as repeating.
Is there a size limit?
No practical one. The converter uses arbitrary-precision integers (JavaScript BigInt), so 64-bit, 128-bit and longer values convert exactly, without rounding.
Why is there no arithmetic in the working?
Every octal digit maps to a fixed group of bits, so conversion is a lookup rather than a calculation.