Subnet Calculator - IP and CIDR

This online subnet calculator is the perfect tool for anyone to size and scale their IPv4 networks.

IP address or CIDR block:

Network Masks
Subnet Mask help
Wildcard Mask help
Host Address Range
First Assignable Host help
Last Assignable Host help
Reserved Addresses
Network Address help
Broadcast Address help
Subnet Properties
# Subnet Bits help
# Assignable Hosts help
Download the free subnet chart PDF to use as a printable reference.

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About the Online Subnet Calculator


Network administrators have been using subnetting for decades to make their networks more manageable and secure. Subnets allow you to break down large networks into smaller pieces called subnets, which are logically independent and isolated from one another. If something goes wrong in one segment of the network, it can be isolated without affecting other segments.

The design of the IP address space means that every time you use an additional bit in your subnet mask, it's broken down into two pieces and assigned to separate networks. This allows you to build and maintain scalable and efficient networks.

Network Calculator and Free API

This online subnet calculator is the perfect tool for anyone who needs to figure out what their network address will be or calculate subnets with masks. This online calculator can help you determine not only whether a network has enough hosts without running into any problems, but also provides an easy way of translating between CIDR notation and dotted-decimal format if needed.

Enter your subnet into this tool and it will tell you the subnet mask, wildcard mask, network address, broadcast address, and number of assignable hosts for your subnet. The results can be edited and saved on an IP address table and printed for reference.

This tool also has a free subnet API to easily do quick subnet calculations from command line or integrate the calculations into your own software. Save a subnet to your NetworkCalc account to manage IP address assignments on your networks.

This calculator and API are designed for systems administrators, network engineers, IT specialists, and students.