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IP Subnet Calculator

Calculate network address, broadcast address, subnet mask, usable IP range and more. Supports IPv4 and IPv6 with CIDR notation, subnet splitting and VLSM planning.

How to use this tool

Steps for using the IP Subnet Calculator.

  1. On Calculator, choose IPv4 or IPv6, type an address such as 192.168.1.77/26 (or pick the prefix from the list) and press Calculate or Enter.
  2. Read the result cards — network, broadcast, masks, first and last usable address, totals — and the Binary Representation, where blue bits are the network and green bits the hosts.
  3. Use Subnet Splitter to cut a network into equal subnets by prefix or by count, and page through the list.
  4. Use VLSM Planner to fit named subnets of different sizes into one block: add each subnet and its host count, then press Generate Plan.
  5. Look up any prefix in Reference Table, and copy results or export them as CSV or JSON from Quick Actions.

Example

A /26 inside 192.168.1.0/24

Input
192.168.1.77/26
Result
Network Address: 192.168.1.64
Broadcast Address: 192.168.1.127
Subnet Mask: 255.255.255.192
Wildcard Mask: 0.0.0.63
First Usable IP: 192.168.1.65
Last Usable IP: 192.168.1.126
Total Addresses: 64
Usable Hosts: 62

Common use cases

  • Working out the gateway, usable range and broadcast address for a new VLAN or VPC subnet.
  • Splitting a /16 or /24 into equal subnets for offices, availability zones or Kubernetes node pools.
  • Planning variable-size subnets (VLSM) so a block isn't wasted on small links.
  • Checking an IPv6 prefix, its first and last address and its expanded form.

How subnet calculations work

An IPv4 address is 32 bits. The prefix length (/26) says how many leading bits belong to the network; the rest number the hosts. Setting every host bit to 0 gives the network address, setting every host bit to 1 gives the broadcast address, and the subnet mask is simply 26 ones followed by 6 zeros (255.255.255.192). The wildcard mask is its inverse, as used in Cisco ACLs.

A conventional subnet loses two addresses — the network and broadcast addresses — so a /26 has 64 addresses and 62 usable hosts. Two prefixes are special: a /31 is a point-to-point link where both addresses are usable and there is no broadcast address (RFC 3021), and a /32 is a single host address.

IPv6 addresses are 128 bits and have no broadcast address, so every address in a prefix can be assigned and the calculator doesn't subtract any. A /64 — the standard size for one LAN — holds 2^64 addresses; counts are computed with exact 128-bit integer arithmetic rather than rounded floating-point numbers.

The address class shown for IPv4 is legacy context only — routing has used CIDR since 1993. Special-purpose blocks (private RFC 1918 ranges, loopback, link-local, CGNAT, documentation, multicast…) are labelled, but whether an address is actually reachable depends on routing, not on this arithmetic. Everything is calculated in your browser.

Limitations

  • The Subnet Splitter and VLSM Planner work on IPv4 networks.
  • Very large splits are shown a page at a time (up to 1,024 rows) so the browser stays fast.
  • The VLSM Planner calculates an address plan; it doesn't configure or reserve anything on a real network.

Frequently asked questions

How many usable hosts does a subnet have?

2 to the power of the host bits, minus 2 for the network and broadcast addresses. A /24 has 256 addresses and 254 usable hosts; a /26 has 64 and 62. The exceptions are /31 (2 usable, RFC 3021) and /32 (a single address). IPv6 prefixes have no broadcast address.

What is the difference between a subnet mask and a wildcard mask?

They are inverses. The subnet mask has ones for the network bits (255.255.255.192 for /26); the wildcard mask has ones for the host bits (0.0.0.63). Wildcard masks are used in Cisco ACLs and OSPF network statements.

Should I type the prefix in the address or pick it from the list?

Either. If you type 192.168.1.77/26, the /26 is used and the prefix list and subnet mask update to match. Without a prefix in the address, the prefix list (or a subnet mask you type) is used.

Why does a /31 have no broadcast address?

RFC 3021 lets point-to-point links use a /31: with only two addresses there is no room for separate network and broadcast addresses, so both are used for the two ends of the link. Most modern routers support it.

Is my IP address sent anywhere?

No. All calculations run in your browser with exact integer arithmetic; nothing you type is sent to a server or stored.