What does the subnet calculator compute?

Given an address and prefix length it returns the network address, broadcast address, usable host range, and total host count for both IPv4 and IPv6.

Why does a /24 show 254 hosts instead of 256?

The network address and broadcast address are reserved, leaving 254 assignable hosts. Point-to-point links often use /31, which reclaims both addresses.

How does IPv6 addressing differ from IPv4 subnetting?

IPv6 subnets are nearly always /64, with enormous address spaces per network. Concepts like broadcast do not exist; multicast and anycast take their place.

Subnet Calculator

Calculate subnet information, divide networks into subnets, and plan IP address allocation.

Subnet Calculation

Enter a network address and specify how you want to divide it

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Subnet Calculator

Calculate subnet information, divide networks into subnets, and plan IP address allocation.

Subnet Calculation

Enter a network address and specify how you want to divide it

Network Address

Calculation Type

Required Subnets

Educational Content

Learn about subnetting, CIDR notation, and network planning concepts

About This Tool

This page provides original, human-reviewed information about subnet calculation, explaining CIDR notation, network and broadcast addresses, usable host ranges, and how to plan subnets without overlap.

What is Subnetting?

Subnetting is the practice of dividing a network into smaller, more manageable sub-networks (subnets). This allows for better organization, improved security, and more efficient use of IP addresses.

Benefits of Subnetting

Improved Security

Isolate different network segments and control traffic flow between them.

Better Organization

Group devices logically by department, function, or location.

Reduced Broadcast Traffic

Smaller broadcast domains mean less network congestion.

Efficient IP Usage

Allocate IP addresses more efficiently based on actual needs.

Key Concepts

Network Address:The first address in a subnet, used to identify the network
Broadcast Address:The last address in a subnet, used for broadcast communications
Subnet Mask:Defines which portion of an IP address is the network and which is the host
Host Range:The usable IP addresses between network and broadcast addresses
CIDR Notation:A compact way to represent IP networks (e.g., /24)

Understanding CIDR Notation

CIDR (Classless Inter-Domain Routing) notation is a method for describing IP networks. The number after the slash (/) indicates how many bits are used for the network portion.