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CIDR notation192.168.1.10/24
Subnet mask255.255.255.0
Wildcard mask0.0.0.255
Network address192.168.1.0
Broadcast address192.168.1.255
First usable host192.168.1.1
Last usable host192.168.1.254
Total addresses256
Usable hosts254
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How it works

  1. Enter an IPv4 address

    Any address within the subnet you want to inspect.

  2. Enter a prefix or subnet mask

    Type a CIDR prefix like 24, or a dotted-decimal mask like 255.255.255.0 — either works.

  3. Read the full subnet breakdown

    Network, broadcast, usable host range, and total addresses all update live.

IP Subnet Calculator breaks down an IPv4 address and prefix into every commonly needed subnet detail: the subnet mask, wildcard mask, network and broadcast addresses, the range of usable host addresses, and the total address count — the same numbers a network engineer works out by hand when planning or troubleshooting a subnet.

The math is pure bitwise arithmetic: the subnet mask marks which bits of the address are "network" bits versus "host" bits, ANDing the address with the mask gives the network address, and OR-ing the network address with the mask's complement (the wildcard mask) gives the broadcast address. The usable host range is everything strictly between those two, since the network and broadcast addresses themselves aren't assignable to individual devices in ordinary subnets.

Two prefix lengths break that general rule on purpose: a /32 has only one address, so there's no room for a separate network/broadcast pair — the single address serves as all three. A /31 has exactly two addresses, and RFC 3021 explicitly designates both as usable endpoints for point-to-point links (like a connection between two routers), rather than wasting half of a tiny 2-address block on an unusable broadcast address the way the general rule would otherwise require.

FAQ

What do "network address" and "broadcast address" mean?
The network address is the first address in the subnet (all host bits zero) and identifies the subnet itself rather than any specific device. The broadcast address is the last address (all host bits one) and is reserved for sending to every host on that subnet at once. Neither is normally assignable to an individual device.
Why do /31 and /32 subnets work differently?
A /32 identifies a single address with no room for a network/broadcast split, so that one address is both. A /31 has exactly two addresses; RFC 3021 defines both as usable point-to-point endpoints (common for router-to-router links) rather than reserving one as a broadcast address the way every larger subnet does.
Can I enter a subnet mask instead of a CIDR prefix?
Yes — the prefix field accepts either a plain number (0-32) or a dotted-decimal subnet mask like 255.255.255.0, which is automatically converted to the equivalent prefix.
Is my data sent anywhere?
No. All subnet math runs locally in your browser.