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Subnet Calculator

Divide a network into multiple equal subnets.

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What Is a Subnet Calculator?

The Subnet Calculator divides a parent IPv4 CIDR block into multiple equal smaller subnets and lists each resulting subnet with its network address, host range, broadcast address, and usable host count. This free online security tool is useful for subnet calculator, subnetting calculator, IP subnet calculator. Common use cases include dividing an IPv4 network into smaller equal subnets and planning host ranges. It is designed for quick browser-based analysis and development workflows. Security checks are signals rather than guarantees, so production systems should also be validated against current standards and their specific threat model.

How to Use This Subnet Calculator

  1. 1
    Enter the network informationProvide the IP address, prefix length, or CIDR block.
  2. 2
    Set the prefixChoose the subnet size that matches your network design.
  3. 3
    Calculate the rangeRun the calculator to derive network and host information.
  4. 4
    Review reserved addressesFor IPv4, check network and broadcast addresses and the resulting usable host range.
  5. 5
    Apply the resultUse the calculated ranges for routing, VLANs, firewall rules, or network documentation.

Frequently Asked Questions

The number of subnets equals 2 raised to the difference between the new prefix and the parent prefix. For example, dividing a /24 into /26 blocks yields four subnets.
A subnet with prefix /p has 2^(32-p) addresses, minus two reserved for the network and broadcast, leaving the usable host count.
This tool currently divides IPv4 blocks. Use the IPv6 Calculator for IPv6 subnet information.

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