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.
FAQ
What does this subnet calculator work out?
From an IPv4 address plus a CIDR prefix or netmask it computes the network and broadcast addresses, usable host range, netmask, wildcard mask, total and usable host counts, and the IP class.
What input formats does it accept?
Either CIDR notation (192.168.1.10/24) or an address with a dotted netmask (192.168.1.10 255.255.255.0), separated by a space or comma.
How does it handle /31 and /32?
A /31 is treated as a 2-address point-to-point link (RFC 3021) with both addresses usable, and a /32 is shown as a single host route.
Is this free and private?
Yes. It's free with no sign-up and all calculations run in your browser; nothing you enter leaves the page or is stored.
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?