The VLSM Calculator: Easily Calculate Subnet Masks

Matthew Fisher - March 14, 2023

Cover image for article: The VLSM Calculator: Easily Calculate Subnet Masks.
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This VLSM calculator takes the guesswork out of subnet calculations and allows you to easily convert a CIDR range into a network.

As a network administrator or engineer, you know how important it is to correctly set up and manage your network's IP addresses. Variable Length Subnet Masking (VLSM) is a crucial component of IP addressing, and it's essential to understand how to use it effectively.

If you're looking for an easy way to calculate subnet masks using VLSM, you've come to the right place. In this article, I'll introduce you to NetworkCalc's VLSM calculator that can help you streamline your IP address calculations.

NetworkCalc: The VLSM Calculator You Can Trust

At NetworkCalc, we understand how important it is to have accurate and reliable tools at your disposal. That's why we created a VLSM calculator and API that is both easy to use and incredibly powerful.

The VLSM calculator takes all of the guesswork out of IP address calculations. With just a few clicks, you can quickly determine relevant details about your network:

  • Subnet mask
  • Wildcard mask
  • CIDR ranges
  • Network address
  • Broadcast address
  • Number of assignable hosts

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How to Use the NetworkCalc VLSM Calculator

Using NetworkCalc's VLSM calculator is incredibly easy. Here's a step-by-step guide to help get you started:

  1. Go to the NetworkCalc website and navigate to the VLSM calculator page.
  2. Enter the IP address or CIDR range for your network in the "IP address or CIDR block" field.
  3. Click the "Calculate" button, and the calculator will do the rest!

In just a few seconds, you'll have all the subnet masks, network addresses, and host ranges you need to set up your network. Try it out below:

Online Subnet Calculator

Use CIDR notation to quickly look up details of IPv4 subnets and CIDR blocks.

Quickly resize your subnet by dragging the slider to the left to decrease the number of subnet bits (which increases the size of each subnet) or right to increase the number of subnet bits (which decreases the size of each subnet).

NetworkCalc vlsm calculator - slider to quickly change subnet size

Using the VLSM Calculator API

In addition to the free online calculators, NetworkCalc has Application Programming Interfaces (APIs) for all of its tools. This means you can perform network calculations from your favorite command-line tool or develop software that integrates network calculations.

Below are some examples for how to calculate the network details from Command Prompt, PowerShell, the MacOS Terminal, or a Linux bash shell. To calculate subnets with command-line tools, use the curl application as shown below, replacing the CIDR range:


The terminal application you use will need Internet access for these calculations.

Other NetworkCalc Tools

In addition to our VLSM calculator, NetworkCalc offers a range of other free online network tools. These include:

Tool API
DNS Lookup DNS APIs - Lookup
SPF Checker DNS APIs - SPF
What is my IP? [no API]
TLS Certificate Lookup Security Tools API
Binary Calculator Binary Converter API
Encoder/Decoder Encoder/Decoder API

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