Octal (base 8) uses digits 0–7. Converting decimal to octal is done by repeated division by 8; it is mostly used for Unix permissions and some older computing systems.
How to use the Decimal 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.
Formula
value = Σ digit × base^positionTo convert: divide repeatedly by the new base and read the remainders in reverse.Worked example
Inputs — Number: 493; Input base: Decimal (10); 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.
Frequently asked questions
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 Decimal to Octal Converter use?
value = Σ digit × base^position.