How to use it
- Type the IPv4 address into IPv4 address, with four numbers separated by dots.
- Read Decimal number: it is the address as one number, which some settings and tools ask for.
- Use Binary to see the bits of each octet, or Hexadecimal, per octet for the usual hexadecimal form.
How an IPv4 address is written
An IPv4 address is 32 bits long. It is made of four octets, and each octet is eight bits, so it can hold a value from 0 to 255 (RFC 791, section 2.3). The dotted decimal notation writes each octet as a decimal number and puts a period between them (RFC 1166, section Network Numbers). For example, 192.168.1.1 has the octets 192, 168, 1 and 1.
The same 32 bits can be read as one number. The first octet holds the highest eight bits, so the number is the first octet times 256 to the power 3, plus the second octet times 256 squared, plus the third octet times 256, plus the fourth octet.
decimal = a x 256^3 + b x 256^2 + c x 256 + d, for the octets a, b, c and dWhich forms the tool writes
Binary and hexadecimal are written per octet, because that is how an address is read by people and by network tools. The hexadecimal number with the prefix 0x is the same 32 bits in one piece, and the octal form writes each octet in base 8 with a leading 0.
A leading zero in a field, such as 001, is read as a decimal number, as the RFC 1166 example does; the tool does not read it as octal. Fields above 255 and addresses with fewer or more than four fields are refused.
The address 192.168.1.1
The four forms of 192.168.1.1 are below. The decimal number is 192 times 256 cubed, plus 168 times 256 squared, plus 1 times 256, plus 1.
| Form | Value |
|---|---|
| Decimal number | 3232235777 |
| Binary | 11000000.10101000.00000001.00000001 |
| Hexadecimal, per octet | C0.A8.01.01 |
| Hexadecimal number | 0xC0A80101 |
| Octal, per octet | 0300.0250.01.01 |
Frequently asked questions
Why is the decimal number so large?
The address is 32 bits, so the largest value is 4294967295, for 255.255.255.255. Each octet adds its value multiplied by a power of 256, so the first octet carries the most weight.
What is the octal form for?
Octal is an older way to write an address. Some tools accept it in dotted notation, where a leading 0 marks the octal digits. The tool writes it per octet, so you can check a value that such a tool shows.
Why does the tool refuse 256 as an octet?
An octet is eight bits, so it holds only 0 to 255 (RFC 791). A value of 256 would need a ninth bit and is not an address of the four-octet form.
Does the tool work for IPv6 addresses?
No. An IPv6 address has 128 bits and its own notation, which the IPv6 tools on this site handle. This tool converts only the 32-bit IPv4 form.
Sources
- RFC 791, Internet Protocol, section 2.3 (Addressing) and the glossary
- RFC 1166, Internet Numbers, section Network Numbers (dotted decimal notation)
Figures and text last checked on Tuesday, November 10, 2026.