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.
Look up DNS records for a hostname like 'example.com'.
Look up security of websites, including SSL and TLS certificates.
Look up registration information for a domain like 'example.com'.
Validate the SPF records for a domain like 'example.com' or the syntax on a
to-be-published SPF record.
Convert between binary, octal, decimal, and hexadecimal.
These tools and their APIs are updated with each release of NetworkCalc. For details on changes, read the release notes.