Network Calculators and APIs

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, including SPF, and SSL certificates.

Try the 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

Use 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

Save and manage your subnets.

Check up on the DNS and security configuration of your website.

Access additional APIs to integrate NetworkCalc's tools in your environment.

Example listing of user-managed subnets

About NetworkCalc

NetworkCalc is a suite of free online resources to help you manage your IP subnets, website security, and home or corporate networks.

We offer a variety of free online calculators, utilities, and Application Programming Interfaces (APIs) for:

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