IPv4 & IPv6 Subnet Calculator

Calculate a CIDR network, address range and subnet mask, or check whether an IP belongs to a subnet. Runs in your browser.

Private addresses work here. Your input stays in this browser and is not sent to our server.

How to use this tool

  1. Enter an address with its prefix, such as 2001:db8::1/64.
  2. Optionally enter another address to check subnet membership.
  3. Select Calculate to see the network and address range.

Understanding the results

IPv4 /31 networks have two point-to-point addresses; /32 has one address. IPv6 has no broadcast address. Address counts are exact, including very large IPv6 networks.

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