IP Addressing Explained: Decimal, Binary, Hex, and Subnets

Every device on a network has an IP address — a numeric label that identifies it uniquely. Understanding how IP addresses are represented in different number bases, and how subnets carve them into ranges, unlocks a lot of networking knowledge.

The structure of an IPv4 address

An IPv4 address is a 32-bit number. It is written as four groups of decimal digits separated by dots — the "dotted decimal" notation:

192.168.1.10

Each group (called an octet) represents 8 bits and can range from 0 to 255.

Notation	Example
Dotted decimal	192.168.1.10
Binary	11000000.10101000.00000001.00001010
Hexadecimal	0xC0A8010A
Unsigned 32-bit integer	3232235786

All four represent the same address. Converting between them is straightforward:

Decimal to binary

Split the address into four octets and convert each 0–255 decimal to an 8-bit binary number:

Octet	Decimal	Binary
1	192	11000000
2	168	10101000
3	1	00000001
4	10	00001010

Full binary: 11000000101010000000000100001010

Decimal to hexadecimal

Convert each decimal octet to a 2-digit hex value:

Octet	Decimal	Hex
1	192	C0
2	168	A8
3	1	01
4	10	0A

Full hex: C0A8010A (often written with 0x prefix: 0xC0A8010A)

IP to integer (and back)

To convert to a single 32-bit unsigned integer, treat the full binary string as a number:

11000000 10101000 00000001 00001010
= (192 × 16777216) + (168 × 65536) + (1 × 256) + 10
= 3221225472 + 11010048 + 256 + 10
= 3232235786

To go back, use bitwise shifts:

octet1 = (3232235786 >> 24) & 0xFF  → 192
octet2 = (3232235786 >> 16) & 0xFF  → 168
octet3 = (3232235786 >> 8)  & 0xFF  → 1
octet4 =  3232235786        & 0xFF  → 10

Use the IP to Decimal Converter and Decimal to IP Converter for quick conversions.

Private and special address ranges

Not all IP addresses are routable on the public internet. RFC 1918 reserves three private ranges:

Range	CIDR	Usage
10.0.0.0 – 10.255.255.255	10.0.0.0/8	Large private networks
172.16.0.0 – 172.31.255.255	172.16.0.0/12	Medium private networks
192.168.0.0 – 192.168.255.255	192.168.0.0/16	Home and small office LANs

Other special ranges:

Address	Purpose
127.0.0.1	Loopback (localhost)
0.0.0.0	Unspecified / "any" address
169.254.0.0/16	Link-local / APIPA (no DHCP)
224.0.0.0/4	Multicast
255.255.255.255	Limited broadcast

CIDR notation and subnets

CIDR (Classless Inter-Domain Routing) notation appends a /prefix to an IP address to describe a network range:

192.168.1.0/24

The /24 means the first 24 bits are the network portion; the remaining 8 bits are host addresses. /24 yields 2⁸ = 256 addresses (254 usable — one for the network address, one for broadcast).

Prefix	Subnet mask	Hosts
/8	255.0.0.0	16,777,214
/16	255.255.0.0	65,534
/24	255.255.255.0	254
/28	255.255.255.240	14
/30	255.255.255.252	2
/32	255.255.255.255	1 (single host)

IPv6 in brief

IPv6 uses 128-bit addresses written as eight groups of four hex digits:

2001:0db8:85a3:0000:0000:8a2e:0370:7334

Consecutive all-zero groups can be collapsed to :: (once per address):

2001:db8:85a3::8a2e:370:7334

IPv6 eliminates the need for NAT and provides ~3.4 × 10³⁸ unique addresses — enough for every atom on Earth to have billions of addresses.

Quick reference

Need	Tool
Convert IP ↔ decimal	IP to Decimal, Decimal to IP
Look up an IP's geolocation	IP Address Lookup
Calculate subnet ranges	CIDR Calculator