Build, Manage, and Monitor Your Domains

Use NetworkCalc's free online network calculators and APIs for home and corporate networking, presented simply.

We offer free REST APIs for system administrators, network administrators, developers, and home network users. Perform network calculations for subnets and convert between binary, decimal, hexadecimal, and octal. Verify your website DNS records, validate SPF records, check your website's SSL certificates, and stay aware of changes that impact your domains.

Use the Free Tools

Online Subnet Calculator

Look up details of IPv4 subnets and CIDR blocks.

DNS Tools

Look up DNS records for a hostname like ''.
DNS Tools

Security Tools

Look up security of websites, including SSL and TLS certificates.
DNS Tools

Binary Converter

Convert between binary, octal, decimal, and hexadecimal.
DNS Tools

Stay Current on Industry News

Keep informed about emerging technologies, security threats, and simple, but effective strategies for building, managing, and monitoring your domains and networks.

Never miss an opportunity to take advantage of more of NetworkCalc's free tools and learn new techniques for improving your people, processes, and technologies.

Integrate the Free APIs

Access free REST APIs for all of the available tools on NetworkCalc. Detailed API documentation is available for the online subnet calculator, DNS tools, security tools, and binary converter.

Additional APIs are available if you register for a NetworkCalc account. This will allow you to save subnets and domains you work with regularly, track the configuration of your website over time, and perform queries quickly.

Get More out of NetworkCalc

NetworkCalc has everything you need to build, manage, and monitor your domains and websites.

We help you simplify domain management with a wide range of easy-to-use tools.

Get access to network APIs that you can integrate into your environment to supercharge your network.

Example listing of user-managed subnets

About NetworkCalc

NetworkCalc is a suite of free online tools and APIs for managing your IP subnets, website security, and home or corporate networks.

The most popular NetworkCalc feature is the subnet API, which enables you to create and manage subnets within your network with ease. With the subnet API, you can quickly perform subnet calculators directly from the command line using Command Prompt, Bash, Python, or any other console with Internet access. See how it works with Command Prompt in the video below:

NetworkCalc's tools are perfect not just for Network Administrators, System Administrators, and Email Administrators, but are also great for IT support, home network users, and students.

Whether you just need to do a quick subnet calculation or you're looking to build, manage, and monitor complex networks, our tools are available to you 24/7.

Try the network tools and remember to bookmark and save and share your favorites:

Online Tools APIs
Subnet Calculator Subnet Calculator API
DNS Lookup DNS Tools API
WHOIS Lookup
SPF Validator
What is my IP?
Security Tools Security Tools API
Binary Converter Binary Converter API
Encoder/Decoder Encoder/Decoder API