What the Subnet Calculator does
A subnet calculator turns CIDR notation into the full picture of a network. CIDR (Classless Inter-Domain Routing) writes an address with a prefix length — the /24 in 192.168.1.0/24 means the first 24 bits identify the network and the remaining 8 bits identify hosts within it.
From that single value this tool derives the network address, the subnet mask, the broadcast address, the first and last usable host, the total number of hosts, and the wildcard mask used in ACLs — everything you need to plan or verify an IP range.
How to read the results
- Network — the base address of the subnet (all host bits zero); it identifies the network itself.
- Subnet Mask — which bits are network vs host, in dotted-decimal (e.g. 255.255.255.0 for /24).
- First / Last Host — the usable range you can assign to devices.
- Broadcast — the all-ones host address; traffic sent here reaches every host on the subnet.
- Total Hosts — usable addresses = 2^(32−prefix) − 2 (network and broadcast are reserved).
Worked example
Input: 192.168.1.10/24
Network 192.168.1.0/24 Subnet Mask 255.255.255.0 First Host 192.168.1.1 Last Host 192.168.1.254 Broadcast 192.168.1.255 Total Hosts 254
A /24 gives 256 total addresses; subtract the network (.0) and broadcast (.255) and you can assign 254 usable host addresses from .1 to .254.
Common use cases
- Plan IP address ranges when designing or segmenting a network.
- Work out how many hosts a given prefix length supports.
- Split a larger block into smaller subnets (VLSM).
- Derive the wildcard mask for router and firewall ACLs.
- Double-check that a device's IP falls inside the intended subnet.