Subnet calculator
Network, broadcast, mask, host range, and host count for any CIDR.
Enter an IPv4 network in CIDR notation (e.g. 192.168.1.0/24) to instantly get the subnet mask, wildcard mask, network and broadcast addresses, the first and last usable host, and the number of usable hosts. All computed locally — nothing leaves your browser request.
Frequently asked questions
What does the /24 in 192.168.1.0/24 mean?
It's the prefix length — how many leading bits are the network portion. /24 means the first 24 bits are the network, leaving 256 addresses (254 usable hosts).
Why are there two fewer usable hosts than addresses?
The network address and the broadcast address are reserved, so a /24 has 256 addresses but 254 usable hosts (except /31 and /32, which have special rules).
How do I split a network into smaller subnets?
Increase the prefix length: a /24 splits into two /25s, four /26s, and so on, each smaller block halving the host count. The calculator shows the resulting ranges so you can carve up address space cleanly.
What's the difference between a netmask and a wildcard mask?
A netmask (255.255.255.0) marks the network bits as 1s; a wildcard mask is its inverse (0.0.0.255) and is what tools like ACLs and OSPF use to match host bits. The calculator shows both.
What are /31 and /32 used for?
A /32 is a single host (one address, often a loopback or a specific route), and a /31 is a special two-address block for point-to-point links where the usual network/broadcast reservation is waived.
How many hosts does each prefix hold?
Usable hosts are 2^(32 − prefix) − 2: a /24 gives 254, a /23 gives 510, a /16 gives 65,534. Each step down in prefix length roughly doubles capacity.
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