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IP Subnet Calculator

Enter an IPv4 address with a CIDR prefix or subnet mask to compute the network and broadcast addresses, usable host range, wildcard mask, total addresses, IP class, and whether it's a private network — all in your browser.

Everything runs in your browser — nothing is uploaded to a server.

Understanding the IP Subnet Calculator

The IP Subnet Calculator is a free, client-side tool for IPv4 network administration. Enter any IPv4 address paired with a CIDR prefix (/0–/32) or dotted-decimal subnet mask; the calculator instantly returns the network address, broadcast address, usable host range, wildcard mask, IP class (A–E), RFC 1918 private-network status, and total/usable host counts. All computation runs in your browser—nothing is sent to a server.

How it works

The calculator parses the IPv4 address and subnet notation (CIDR or mask) into 32-bit integers. It applies bitwise AND with the network mask to extract the network address, applies bitwise OR with the wildcard (inverted mask) to derive the broadcast address, and counts hosts using 2^(32 − prefix). For /31 (RFC 3021 point-to-point), both addresses are usable; for /32, only the host itself; for all others, total addresses minus 2 (network and broadcast). It validates mask contiguity by inverting and checking that the result is a power of two. The tool also detects RFC 1918 private ranges (10/8, 172.16/12, 192.168/16) and classifies by first octet.

Network Address = IP AND SubnetMask Broadcast Address = Network Address OR WildcardMask Usable Hosts = 2^(32 − CIDR prefix) − 2 (except /31 = 2, /32 = 1) Wildcard Mask = ~SubnetMask

Worked example

Input: 192.168.1.10 with /24 (or 255.255.255.0). Output: Network 192.168.1.0, Broadcast 192.168.1.255, first usable host 192.168.1.1, last usable host 192.168.1.254, 256 total addresses, 254 usable hosts. The tool also reports Class C, Private (RFC 1918: Yes), and Wildcard Mask 0.0.0.255.

Tips & common mistakes

  • CIDR (/24) and subnet-mask (255.255.255.0) modes are interchangeable—switch tabs to input whichever notation you prefer.
  • The /31 prefix is a special case (RFC 3021): both addresses in a /31 block are usable, often for point-to-point router links.
  • Always verify the broadcast address: it is the last address in the subnet, not a usable host address.
  • The wildcard mask (inverse of subnet mask) is commonly used in access-control lists (ACLs) on routers and firewalls.
  • Private IP ranges (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16) will show 'Private (RFC 1918): Yes'—only these are valid for internal networks.
  • Results can be copied to clipboard as plain text with the 'Copy results' button, useful for pasting into documentation or network configs.

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Frequently Asked Questions

What does /24 mean?

A /24 is a 24-bit network prefix, which corresponds to the mask 255.255.255.0. It defines a block of 256 IP addresses, of which 254 are usable for hosts because one address is the network address and one is the broadcast address.

Does it show the broadcast address and host range?

Yes. For any IPv4 address and prefix, the calculator returns the network address, broadcast address, and the first and last usable host, along with the total addresses and usable host count.

Does it detect private IP addresses?

Yes. It flags addresses in the RFC 1918 private ranges — 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16 — so you can tell at a glance whether an address is private or public.