Is my network data sent to a server?

No. The whole calculation is done in your browser with plain JavaScript bitwise math. No IP address or network detail ever leaves your device.

Why are usable hosts two fewer than total addresses?

In a normal subnet the first address is reserved as the network address and the last as the broadcast address, so they cannot be assigned to hosts. The /31 and /32 prefixes are special cases handled accordingly.

What is a wildcard mask?

A wildcard mask is the bitwise inverse of the subnet mask. It is used in tools like access-control lists to specify which bits of an address can vary, and the calculator derives it automatically.

How many hosts does a /24 hold?

A /24 has 256 total addresses (2^8), of which 254 are usable hosts after removing the network and broadcast addresses. More generally, usable hosts = 2^(32 − prefix) − 2.

How do I find the network address?

The network address is the IP bitwise-ANDed with the subnet mask, which zeroes out all the host bits. The broadcast address sets all those host bits to 1 instead.

What are /31 and /32 used for?

A /32 is a single host (used for loopbacks and host routes) and a /31 is a two-address point-to-point link per RFC 3021, where both addresses are usable because there is no room for separate network and broadcast addresses.

IP Subnet / CIDR Calculator

IP subnet and CIDR calculator

Enter an IPv4 address in CIDR notation — for example 192.168.1.10/24 — and instantly get the network address, broadcast address, usable host range, subnet mask, wildcard mask, and total address count. Network engineers use this to plan address space and verify firewall and routing config.

How it works

The prefix length (the number after the slash) sets how many leading bits are the network portion. The calculator builds a 32-bit mask of that many 1-bits, then:

Network address = IP AND mask (host bits zeroed)
Broadcast address = network OR wildcard (host bits set to 1)
Wildcard mask = bitwise NOT of the subnet mask
Usable hosts = 2^(32 − prefix) − 2 (the /31 and /32 special cases keep both addresses)

Example

For 192.168.1.10/24:

Field	Value
Subnet mask	255.255.255.0
Network address	192.168.1.0
Broadcast address	192.168.1.255
Usable host range	192.168.1.1 – 192.168.1.254
Total addresses	256
Usable hosts	254

All of the math is bitwise arithmetic done in your browser, so no address or network detail is ever uploaded.