Subnet Calculator - IP and CIDR

Network Masks


Host Address Range


Reserved Addresses


Subnet Properties

Download the free subnet chart PDF to use as a printable reference.

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About the Online Subnet Calculator


Subnetting is a fundamental tool in any network administrator's arsenal because it allows you break large networks into smaller pieces called subnets. This makes network management easier by creating segments of your network that are logically independent and isolated from one another. A failure in one subnet can be isolated and you can create different routing and firewall rules for different subnets for better network security.

Each additional bit you use results in the network being split into two pieces with half as many IP addresses each. This allows you to engineer and maintain scalable and efficient networks.

Network Calculator and Free API

The online subnet calculator allows you to quickly calculate the network details for an IPv4 address or CIDR block. Use this free online calculator to determine subnet mask, wildcard mask, network address, broadcast address, and assignable hosts. Use this tool as a subnet mask calculator to translate between CIDR notation and dotted-decimal notation for subnet masks.

View the results in an editable IP subnet table or print the details for reference. This tool has a free API that allows you to integrate subnet calculations in your own software. Save a subnet to your NetworkCalc account to easily keep track of IP addresses on your networks.

The calculator and API are free to use and are ideal for systems administrators, network administrators, Information Technology specialists, and students.