Every bit, accounted for.
Turn an IP address into a clear picture of its network.
Build your subnet
Host, CIDR, or address/subnet-mask.
Use /24 or 24. CIDR in the address takes priority.
Start anywhere in a subnet.
We’ll find the network boundary.
192.168.10.0/24
192.168.10.42 belongs to this network.
Divide this network
Split evenly or fit networks of different sizes. Export a temporary plan as CSV.
Subnet planner ＋
Temporary plan · nothing is saved. Export before leaving this page.
IPv6 LANs normally use /64.
One per line: Name, host count or Name, /prefix. Largest first. Host counts use ordinary IPv4 LAN sizing; enter /31 explicitly for a point-to-point link. IPv6 uses prefixes.
Keep existing allocations
Green: planned · grey: existing · pale: free. Tiny allocations may be too small to see.
| Name / status | Network | First host / address | Last host / address | Usable hosts |
|---|
Ranges show subnet capacity. Special-use address rules still apply. IPv6 capacity is not a guaranteed count of assignable hosts.
How to read these results ＋
Allocation is not reachability. Public routable means eligible for global routing. This offline calculator cannot prove a live BGP announcement or that a host responds. Bogon matches come from a dated snapshot, not a live route check.
IPv6 has no broadcast. The displayed range is the mathematical address range. Not all addresses are assignable to ordinary hosts: subnet-router anycast and other reserved interface IDs depend on subnet type. /127 point-to-point and /128 single-address networks are handled separately.
Classful capacity is historical. IPv4 Class A, B and C parents use /8, /16 and /24. IPv6 is classless. Modern networks use CIDR.
Open an address from a link. Use /?ip=10.0.7.7/30 or /10.0.7.7/30. Subnet masks, IPv6 prefixes, and explicit wildcard: masks work too. If both are present, the ip query value wins.