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Results
Conventional subnets exclude network and broadcast addresses. /31 uses two addresses on a supported point-to-point link; /32 identifies one address. This is not a DHCP-pool or reachability measurement.
Worked example: 192.168.1.37/24
/24 keeps the first 24 bits as the network part. The remaining 8 bits represent 256 addresses. The example produces network 192.168.1.0/24, mask 255.255.255.0 and last address 192.168.1.255. In a conventional subnet, excluding the network and broadcast addresses leaves 254 host addresses.
The input .37 is a device address, so normalization to .0 is expected. A wildcard mask reverses the subnet-mask bits: here it is 0.0.0.255. A wildcard is not itself a CIDR prefix; check which notation your configuration field accepts.
/31, /32 and host-count exceptions
Under RFC 3021, a /31 can use both addresses on a supported point-to-point link. The calculator therefore shows two host addresses and no broadcast. That does not imply that an ordinary router LAN supports /31. A /32 describes one address or host route and is shown as one host address.
/0 covers all 4,294,967,296 IPv4 addresses. The host count follows address arithmetic; it does not subtract special-purpose reservations or reflect an actual DHCP pool or device count. IPv6 and non-contiguous masks are outside this IPv4 calculator.
Before changing a setting
Record the existing mask before comparing a new subnet. Overlapping ranges can cause VPN or routing conflicts. Do not turn calculator output into an unrestricted firewall allow rule. Prefer the smallest range needed, including a /32 when only one IPv4 endpoint should be allowed.
Calculations run in browser memory. Inputs are not transmitted, stored or put into the URL, and this page has no advertising or visit-analytics scripts. Reloading resets the input. Check the actual equipment documentation and your administrator before applying a change.