Use this network utility to parse, normalize, convert, or derive IPv4, IPv6, subnet, reverse-DNS, or MAC addressing information under a stated prefix convention.

CIDR prefix

Required integer input.

Compute assignable IPv4 host addresses from a CIDR prefix, including /31 point-to-point and /32 host routes. The tool evaluates the supplied inputs together and returns the named outputs below; it does not infer omitted operating conditions or change the units shown.^[1]

Usable hosts

The resulting usable hosts returned as an integer.

• Syntax and arithmetic validity do not establish reachability, ownership, routing, DNS, privacy, or authorization. IPv4 special-use ranges, IPv6 scopes and compression, prefix boundaries, mapped forms, and host-count conventions require explicit handling.
• Use finite inputs in the displayed units and preserve more precision than the final presentation requires. Independently verify safety-critical, financial, compliance, or production decisions.

Validate against current IANA registries and the target platform, test boundary prefixes, and use live network tools only with appropriate authorization.

• IPv4 CIDR Calculator

  Compute network address, broadcast, host range, and capacity for an IPv4 CIDR block.

• IPv6 Subnet Calculator

  Expand an IPv6 address, apply a prefix length, and derive the first address, last address, and exact address count. IPv6 has no broadcast address and does not subtract network or broadcast addresses from a prefix.

• Netmask to Prefix

  Convert a dotted-decimal IPv4 netmask into its CIDR prefix length.