IP Address Calculator — Calculate Network and Host Ranges

An IP address calculator takes an IP address and subnet mask (or CIDR notation) and tells you: the network address, broadcast address, first usable IP, last usable IP, and total host count. These values define the boundaries of a subnet.

Use the Subnet Calculator for instant IP range calculations from any CIDR block or subnet mask.

The four key values

For any subnet, you need to know:

1. Network address — the first IP in the range (host bits all 0)
2. Broadcast address — the last IP in the range (host bits all 1)
3. First usable host — network address + 1
4. Last usable host — broadcast address - 1

For 192.168.1.0/24:

• Network: 192.168.1.0
• Broadcast: 192.168.1.255
• First host: 192.168.1.1
• Last host: 192.168.1.254
• Usable hosts: 254

The calculation step by step

Input: 10.0.5.67/22

Step 1: Convert CIDR to subnet mask

/22 → 22 ones followed by 10 zeros
11111111.11111111.11111100.00000000
= 255.255.252.0

Step 2: Find the network address (AND operation)

IP:   10.0.5.67   = 00001010.00000000.00000101.01000011
Mask: 255.255.252.0 = 11111111.11111111.11111100.00000000
AND:  10.0.4.0    = 00001010.00000000.00000100.00000000

Network address: 10.0.4.0

Step 3: Find the broadcast address (OR with inverted mask)

Network: 10.0.4.0    = 00001010.00000000.00000100.00000000
Inv mask: 0.0.3.255  = 00000000.00000000.00000011.11111111
OR:  10.0.7.255      = 00001010.00000000.00000111.11111111

Broadcast: 10.0.7.255

Step 4: Usable range

First host: 10.0.4.1
Last host:  10.0.7.254
Usable hosts: 2^10 - 2 = 1,022

10.0.5.67 is inside this range, confirming it’s a valid host in the 10.0.4.0/22 subnet.

Checking if an IP is in a subnet

import ipaddress

# Check if IP is in a network:
network = ipaddress.ip_network('10.0.4.0/22')
ip = ipaddress.ip_address('10.0.5.67')

print(ip in network)  # True
print(ipaddress.ip_address('10.0.8.1') in network)  # False

# Full network info:
print(network.network_address)   # 10.0.4.0
print(network.broadcast_address) # 10.0.7.255
print(network.netmask)           # 255.255.252.0
print(network.num_addresses)     # 1024
print(list(network.hosts())[0])  # 10.0.4.1  (first usable)
print(list(network.hosts())[-1]) # 10.0.7.254 (last usable)

// Using ip-address library:
const { Address4 } = require('ip-address');

const network = new Address4('10.0.4.0/22');
const ip = new Address4('10.0.5.67');

console.log(network.isInSubnet(ip));     // True (ip in network)
console.log(network.startAddress().address); // '10.0.4.0'
console.log(network.endAddress().address);   // '10.0.7.255'

Common subnets and their ranges

Subnetting a network

Dividing a larger network into smaller subnets is the core of network design.

Example: Split 10.0.0.0/24 into 4 equal subnets.

4 subnets requires 2 bits (2² = 4). Borrow 2 bits from the host portion: /24 + 2 = /26.

10.0.0.0/26   → 10.0.0.0 – 10.0.0.63    (hosts: 62)
10.0.0.64/26  → 10.0.0.64 – 10.0.0.127  (hosts: 62)
10.0.0.128/26 → 10.0.0.128 – 10.0.0.191 (hosts: 62)
10.0.0.192/26 → 10.0.0.192 – 10.0.0.255 (hosts: 62)

4 subnets × 62 hosts + 4 × 2 reserved (network/broadcast) = 256 total, matching the original /24.

IP classes (historical context)

Before CIDR, IP addresses were divided into classes:

Classful addressing wasted massive amounts of address space (a Class A block with 16M addresses assigned to a company needing 500 hosts). CIDR replaced classful addressing to allow variable-length subnet masks and reclaim address space.

Today, classes are mostly historical references. You may hear “Class C range” when someone means a /24 block — it’s technically imprecise but widely understood.

AWS, Azure, and GCP IP calculators

Cloud networking uses the same IP calculation rules. In AWS VPCs:

• AWS reserves 5 IPs per subnet: network address, router IP, DNS IP, reserved for future, broadcast address
• Usable hosts = 2^host_bits - 5
• A /24 subnet has 256 - 5 = 251 usable host IPs

The Subnet Calculator shows both the standard 2-reserved and 5-reserved (AWS) host counts.

Related tools

• Subnet Calculator — calculate network ranges and host counts
• CIDR Notation — what /24, /16, /8 mean
• Private IP Address Ranges — RFC 1918 address ranges