IPv4 subnet calculator
Find the network, subnet mask, broadcast address, and host range for an IPv4 address and CIDR prefix. The calculator handles /31 point-to-point links and /32 routes separately.
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Calculation code runs locally in your browser and does not submit these fields. Shared links include your inputs after the # sign; do not share private network details.
Example: 192.168.50.130/26
A /26 contains 64 addresses. This address belongs to 192.168.50.128/26, with mask 255.255.255.192. The conventional host range is 192.168.50.129 through 192.168.50.190; 192.168.50.191 is the directed broadcast address. That leaves 62 host slots before any gateway, DHCP exclusions, or platform reservations.
What the result means
The prefix fixes the network bits; the remaining bits give 232 − prefix addresses. The network is the aligned beginning of that block. For prefixes through /30, this tool excludes the first and last address when showing the conventional host range. A wildcard mask is the inverse of the subnet mask; it is shown for reference, not as a ready-to-deploy firewall rule.
A /31 is treated as a two-endpoint point-to-point link under RFC 3021. There is no directed broadcast address on that link. Both devices must support this use; it is not a suggestion to configure a two-address ordinary LAN. A /32 identifies one address.
This is address arithmetic, not an allocation or reachability check. It does not inspect your network, detect overlaps, choose a gateway, or make reserved and special-purpose ranges usable. Cloud providers can reserve additional addresses. A /0 calculation describes the entire IPv4 block, not a usable LAN.
If you are planning an off-site backup over that network, the backup-window calculator checks whether the daily transfer fits the time available.