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CIDR Calculator & IP Subnet Inspector

Calculate IPv4 or IPv6 network boundaries.

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Network to calculate

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Test one address against the calculated block. This performs no connection or lookup.

Network calculation

Calculate a network to see its boundaries.

The normalized block, address range, mask and context will appear here.

Investigate keeps only the value you choose in this tab for the extension handoff.

How to use it

  1. 1

    Enter an address or block

    Use an IPv4 or IPv6 address with a prefix, such as 192.0.2.130/26 or 2001:db8::1/64. A bare address is treated as a host route.

  2. 2

    Calculate the network

    Review the normalized block, exact address range, mask and special-use context. You can also test one address for membership.

  3. 3

    Continue with selected evidence

    Copy a calculated value or explicitly hand the entered address or normalized CIDR block to Coeus for investigation.

What the results mean

Network math is not a reputation result.

The calculation does not query WHOIS, routing, DNS, geolocation or threat intelligence, and it does not establish ownership or maliciousness.

Special-use context applies to the entered address.

The label identifies known reserved or local-purpose ranges. Public or unclassified does not prove that an address is allocated, reachable or trustworthy.

Usable IPv4 hosts depend on the network.

The conventional host count excludes network and broadcast addresses through /30, treats /31 as point-to-point and /32 as one host. Local policy can differ.

Related tools

Keep working with the same local-first toolkit.

IOC ExtractorFind, deduplicate and review identifiers in text.URL ParserRead URL structure and reveal supported Safe Links destinations.