IP Subnet CalculatorIP Subnet Calculator
Enter an IPv4 or IPv6 address in CIDR notation (or address + netmask) and get the full subnet breakdown instantly.
Binary breakdown (| marks the network/host boundary)
Split this subnet
How many IPs do you need?
Enter the number of devices/addresses and get the right subnet size (IPv4).
Rule of thumb: pick the size with growth headroom — renumbering later costs far more than the spare addresses.
For IPv6, host count is irrelevant: every LAN gets a /64 regardless of size.