Our free subnet calculator is an essential tool for network administrators, IT professionals, and students studying networking. Enter an IP address and subnet mask (or CIDR notation) to instantly calculate the network address, broadcast address, first and last usable host addresses, number of usable hosts, wildcard mask, and IP class.

Subnetting is the process of dividing a network into smaller sub-networks (subnets) to improve performance, security, and address efficiency. Whether you are designing a corporate network, studying for a networking certification, or troubleshooting a network issue, this subnet calculator provides all the information you need instantly.

🌐 Subnet Calculator

🌐 Subnet Information

Network Address
Broadcast Address
First Usable Host
Last Usable Host
Usable Hosts
Subnet Mask
Wildcard Mask
CIDR
IP Class

How to Use the Subnet Calculator

Calculating subnet information is straightforward:

  1. Enter an IP address in standard IPv4 dotted-decimal notation (e.g., 192.168.1.0).
  2. Enter the subnet mask in either CIDR notation (e.g., /24) or dotted-decimal (e.g., 255.255.255.0).
  3. Click Calculate Subnet to see all network information.

When Should You Use a Subnet Calculator?

Use the subnet calculator when designing or troubleshooting IPv4 networks. In particular, it is invaluable when planning IP address allocation for a corporate network — helping you determine how many hosts can exist on each subnet and how to efficiently divide your address space. Furthermore, it is essential when studying for networking certifications such as CompTIA Network+, Cisco CCNA, or equivalent qualifications.

Additionally, network engineers use subnet calculators when configuring routers, firewalls, and switches. Moreover, system administrators use it to verify network configurations and diagnose connectivity issues related to incorrect subnet masks or IP address conflicts.

Subnetting Quick Reference

Here is a quick reference for the most common CIDR subnet sizes:

  • /24 (255.255.255.0) — 254 usable hosts. The most common subnet for small networks.
  • /25 (255.255.255.128) — 126 usable hosts. Splits a /24 into 2 equal subnets.
  • /26 (255.255.255.192) — 62 usable hosts. Four subnets from one /24.
  • /27 (255.255.255.224) — 30 usable hosts. Eight subnets from one /24.
  • /30 (255.255.255.252) — 2 usable hosts. Used for point-to-point router links.

Frequently Asked Questions About the Subnet Calculator

What is CIDR notation?

CIDR (Classless Inter-Domain Routing) notation expresses a subnet mask as a prefix length — the number of bits set to 1 in the mask, written after a slash. For example, /24 means 24 bits are the network portion, equivalent to 255.255.255.0. A /24 provides 256 addresses with 254 usable hosts.

How many hosts can a /24 subnet support?

A /24 subnet has 256 total addresses (2^8). Subtracting the network address and broadcast address leaves 254 usable host addresses.

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Disclaimer: For informational and educational purposes only. Always verify network configurations in your actual network environment.