Acutis Subnet / CIDR calculator
Enter an IPv4 address with a CIDR prefix (192.168.1.10/24) or a dotted netmask (192.168.1.10 255.255.255.0). Everything is computed in your browser — nothing leaves this page.
Accepts ip/cidr or ip mask (space or comma separated). Handles /31 (point-to-point) and /32 (single host) sensibly.
What each value means
- Network address — the first address in the block; identifies the subnet itself, not a host.
- Broadcast address — the last address; packets sent here reach every host on the subnet.
- Usable host range — the addresses you can actually assign to devices (network and broadcast excluded).
- Wildcard mask — the inverse of the netmask; used in ACLs and OSPF on Cisco-style gear.
- /31 — a 2-address point-to-point link (RFC 3021); both addresses are usable. /32 is a single host route.
The math checks out — but does the subnet?
A correct subnet on paper still breaks when a duplicate IP, a wrong gateway or a rogue DHCP server is on the wire. Acutis Go runs the full check — network, DNS and your own machine — in 60 seconds and tells you plainly where the fault is. Free.
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Related guide: What is a subnet?