NetworkCalc is a suite of network tools and APIs to help you manage your domain, website, and IPv4 networks.

The tools are free for unlimited use - try them out below. To get access to more tools and functionality, register for a NetworkCalc account.

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

WHOIS Lookup

Look up registration information for a domain like ''.
WHOIS Lookup

SPF Checker

Validate the SPF records for a domain like '' or the syntax on a to-be-published SPF record.
SPF Lookup

What is my IP?

Look up your IP address that is used publicly.
What is my IP

Binary Converter

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


Encode and decode using different encoding schemes: URL, Base64, and Base64URL.

These tools and their APIs are updated with each release of NetworkCalc. For details on changes, read the release notes.