# Binary to Octal Converter

URL: https://speedycalculator.com/calculators/conversion/binary-to-octal/
Last updated: 2026-10-25

> The binary to octal converter converts whole numbers between binary, octal, decimal and hexadecimal, groups binary digits in fours, counts the bits needed and shows the two’s-complement form for a chosen bit width. It works with numbers of any length. Everything is calculated in your browser; nothing you type is sent to our server.

## Inputs

- Number
- Input base
- Convert to
- Two’s complement width

## Results

- Result
- Binary
- Octal
- Decimal
- Hexadecimal
- Bits needed
- Two’s complement

## Formula

```
value = Σ digit × base^position
To convert: divide repeatedly by the new base and read the remainders in reverse.
```

## Explanation

Octal groups binary digits in threes, so each octal digit stands for exactly 3 bits. It is still used for Unix file permissions, where 111 101 101 is chmod 755.

### How to use the Binary to Octal Converter

- **Number**
- **Input base**
- **Convert to**
- **Two’s complement width**

Everything runs in your browser, so results appear instantly and nothing you type is sent to a server.

### How it works

The number is read exactly using arbitrary-precision integers (so very long values are not rounded), then written in each base. Two’s complement shows how a negative number is stored in the chosen number of bits.

## Worked example

Inputs — Number: 111101101; Input base: Binary (2); Convert to: Octal (8); Two’s complement width: No fixed width.

Results — **Result = 755**; Binary = 1 1110 1101; Octal = 755; Decimal = 493; Hexadecimal = 1ED; Bits needed = 9.

## Key terms

- **Bit**: A binary digit, 0 or 1.
- **Nibble**: Four bits, one hexadecimal digit.
- **Two’s complement**: The standard way computers store negative integers.

## FAQ

**What is 255 in binary?**
1111 1111.

**What is FF in decimal?**
255.

**How do I convert binary to hex by hand?**
Split the bits into groups of four from the right and replace each group with its hex digit (0000 = 0 … 1111 = F).

**What formula does the Binary to Octal Converter use?**
value = Σ digit × base^position.