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Subnet Calculator

Calculate subnet details from an IPv4 address and prefix length or subnet mask.

How to Use This Tool

  1. Enter an IPv4 address (e.g. 192.168.1.100).
  2. Enter the prefix length (e.g. 24) or subnet mask (e.g. 255.255.255.0).
  3. View the calculated network address, broadcast, first and last host, and total hosts.

Learn More About Subnet Calculator

Understanding Subnets

A subnet divides a larger network into smaller segments. The subnet mask (or prefix length) defines how many bits belong to the network and how many to the host. The network address is the first address in the range; the broadcast address is the last. Usable host addresses are between the first host and the last host (inclusive).

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About Subnet Calculator

The Subnet Calculator helps network administrators and developers determine key subnet information from an IPv4 address and prefix length or subnet mask. It computes the network address, broadcast address, first and last usable host, and the total number of usable hosts—essential for planning and configuring networks.
Calculate IPv4 subnet details from an IP and prefix or mask.
Platform
Web-based
Cost
Free
IPv4 only
Yes

Examples

Class C subnet

Calculate a /24 subnet for 192.168.1.0.
Input
IP: 192.168.1.0, Prefix: 24
Output
Network: 192.168.1.0, Broadcast: 192.168.1.255, Usable hosts: 254

Small subnet

Calculate a /28 subnet.
Input
IP: 10.0.0.1, Prefix: 28
Output
Network: 10.0.0.0, First host: 10.0.0.1, Last host: 10.0.0.14, Broadcast: 10.0.0.15, Usable: 14

Features

Prefix or Mask

Input either CIDR prefix (e.g. /24) or dotted subnet mask.

Full Subnet Info

Shows network, broadcast, first/last host, and host count.

Instant Results

Calculations run in the browser with no server required.

Use Cases

  • Plan subnets and allocate IP ranges.
  • Configure firewalls and ACLs with correct ranges.
  • Verify network and broadcast addresses for an IP and mask.
  • Learn how subnetting works with real examples.

Frequently Asked Questions

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