About IP Address Calculator

A full IPv4 subnet calculator. Takes an address and CIDR prefix (or pasted CIDR notation) and computes the network and broadcast addresses, subnet and wildcard masks, usable host range, and usable/total host counts — with correct handling of /31 point-to-point links (2 usable hosts, RFC 3021) and /32 host routes (1 host). It classifies the address against RFC special-use ranges (private RFC 1918, CGNAT RFC 6598, loopback, link-local, documentation TEST-NET, multicast, reserved), shows the network address in binary with the prefix boundary marked, and includes a Subnet Splitter that divides the block into equal smaller subnets for VLAN and Azure subnet planning.

• Bitwise math: IP AND mask = network; network OR wildcard = broadcast (verified for /0–/32)
• Correct edge cases: /31 = 2 usable hosts (RFC 3021), /32 = 1 host route — not the naive 2^n−2
• Special-use classification: RFC 1918 private, RFC 6598 CGNAT, loopback, link-local, TEST-NET docs, multicast, reserved, else Public
• Subnet Splitter: enter a longer prefix to enumerate the resulting equal subnets with their broadcast and usable range
• Accepts CIDR notation pasted into the IP field (192.168.1.0/24) and a separate prefix input
• Binary network address shown with a | at the network/host bit boundary; copy buttons on every field
• Wildcard mask provided for ACL and OSPF use; reference table of common /8–/32 masks

Frequently Asked Questions

How are /31 and /32 handled?

A /31 reports 2 usable hosts — per RFC 3021 both addresses are usable on point-to-point links (no network/broadcast reservation). A /32 reports a single host route. This avoids the misleading “0 usable” the naive 2^n−2 formula produces.

What is the Subnet Splitter for?

Enter a prefix longer than your network’s (e.g. split a /24 into /26s) and it lists every resulting subnet with its network, broadcast, usable range, and host count — exactly what you need when carving a VNet or VLAN range into smaller subnets.

What does the scope badge mean?

It classifies the address against IANA/RFC special-use ranges — Private (RFC 1918), CGNAT (RFC 6598), Loopback, Link-local, Documentation (TEST-NET), Multicast, Reserved — or Public if it falls outside all of them.

Can I paste CIDR notation?

Yes. Paste 192.168.1.0/24 into the IP field and the tool splits off the /24 into the prefix input automatically. A subnet mask /24 and 255.255.255.0 are equivalent representations.