How are usable hosts calculated?

For standard subnets (/1 to /30), usable hosts = (2^(32 - CIDR)) - 2. The -2 accounts for the reserved network and broadcast addresses. /31 (RFC 3021) has 2 usable point-to-point hosts, and /32 is a single host route.

What is a Wildcard Mask?

A Wildcard Mask is the bitwise inverse of the Subnet Mask (e.g. Subnet Mask 255.255.255.0 has a Wildcard of 0.0.0.255), commonly used in Cisco ACLs and OSPF configurations.

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IPv4 CIDR Subnet Calculator

Calculate network address, broadcast, usable IP range, netmask, and wildcard mask with binary breakdown.

IP Address

Subnet Mask / CIDR Prefix

Network Address (ID)

192.168.1.0

Broadcast Address

192.168.1.255

Usable Hosts

254

Network Scope

Private (RFC 1918)

Usable Host Range

192.168.1.1 → 192.168.1.254

Subnet Mask

255.255.255.0

Wildcard Mask

0.0.0.255

Total Addresses

256

IP Class

Class C

Binary Breakdown (32-bit)

IP (Binary)11000000.10101000.00000001.01100100

Mask (Binary)11111111.11111111.11111111.00000000

Network (Binary)11000000.10101000.00000001.00000000

Broadcast (Binary)11000000.10101000.00000001.11111111

Common CIDR Subnets

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Understanding IPv4 CIDR & Subnet Calculations

Technical architecture and practical engineering workflows

CIDR (Classless Inter-Domain Routing) notation uses a prefix (like /24) to denote how many bits of a 32-bit IPv4 address represent the network identifier, leaving the remaining bits for host addresses.

Our subnet calculator applies bitwise operations on the 32-bit integer representation of the IP address against the subnet mask to determine the Network ID (Bitwise AND), Broadcast ID (Bitwise OR with inverted mask), and all assignable host IPs.

Step-by-Step Execution Guide

1. Enter IPv4 & Prefix

Type an IP like 192.168.1.10 and choose a CIDR prefix (e.g. /24).

2. Instant Bitwise Calculation

View network ID, broadcast address, netmask, wildcard, and usable range.

3. Inspect Binary Breakdown

Compare octets in binary format to visualize subnet boundaries.

Frequently Asked Questions

Frequently asked technical questions and specs

The Network Address (first IP in the block) identifies the subnet itself. The Broadcast Address (last IP in the block) is used to send packets to all hosts on the subnet. Neither can be assigned to individual devices.

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