Binary to Octal Calculator
Convert a binary number into octal. Enter a string of 0s and 1s and this calculator groups the bits into threes (from the right) and turns each group into a single octal digit, 0–7.
Formula
octal = binary value converted from base-2 to base-8
- The binary number is read as a base-2 value and rewritten in base-8.
- A handy shortcut: group the bits into threes starting from the right, then convert each group to a single octal digit (000–111 maps to 0–7).
- Octal digits run 0 through 7 only — there is no 8 or 9.
- Enter only the digits 0 and 1. A leading '0b' prefix is accepted and ignored.
- Octal is convenient because each digit represents exactly three bits.
101101 in octal
Inputs
- Binary Number: 101101
Grouped into threes from the right: 101 101. 101 = 5 and 101 = 5, so 101101₂ = 55 in octal (decimal 45).
Frequently asked questions
How do I convert binary to octal by hand?
Group the bits into sets of three starting from the right (pad the left with zeros if needed), then convert each three-bit group to its single octal digit.
Why three bits per octal digit?
Because 8 is 2 to the third power, every group of three bits maps cleanly to exactly one octal digit (0–7).
What digits does octal use?
Octal uses only 0 through 7. The values 8 and 9 do not exist in base-8.
What if my binary length is not a multiple of three?
Pad the left end with zeros until it is. For example, 101101 is already six bits, so it groups neatly as 101 101.
Can I enter a '0b' prefix?
Yes. A leading 0b is stripped automatically, so 0b101101 and 101101 give the same octal value.