IPv4 Subnet Calculator
Enter any IPv4 address and CIDR prefix — or type the dotted-decimal mask and let the CIDR update automatically. Get the full subnet breakdown instantly: network and broadcast addresses, usable host range, wildcard mask, IP class, address type and a colour-coded binary view that shows exactly which bits are network vs host. Correct edge-case handling for /31 (RFC 3021 point-to-point) and /32 (single host).
CIDR and subnet mask stay in sync — change either one.
Binary representation
■ Network bits · ■ Host bits
Is an IP in this subnet?
Enter any IPv4 address to check if it falls within the current network.
Need help with your network?
From subnetting to full network design — Peritus Digital can help.
Our Newcastle team designs and manages networks for Hunter Region businesses — VLANs, firewall rules, SD-WAN, structured cabling and everything in between. If you're sizing subnets, chances are you're planning infrastructure. Let's talk.