Subnet Splitter
Split an IPv4 CIDR block into smaller equal-size subnets with copyable network details.
Enter an IPv4 CIDR block, then split it into equal-size child subnets by target prefix length or by a power-of-two subnet count. The output is calculated locally and is intended for address planning, documentation, and change reviews.
Host addresses are normalized to the containing network. IPv6 subnet planning is not supported by this tool.
Count mode requires a power of two so every child subnet is the same size.
How it works
IPv4 subnet splitting starts with the parent network boundary and prefix length. A longer target prefix creates smaller child networks, and each extra prefix bit doubles the number of equal-size subnets.
Count mode is limited to powers of two because equal-size CIDR splits cover the parent block cleanly only when the child subnet count is a power of two. The row limit keeps very large splits usable in the browser while showing how many additional rows were omitted.
For /31 and /32 child subnets, endpoints are shown as usable for point-to-point and host-route planning. The tool does not test reachability, routing policy, reservations, or whether an address block is assigned to your organization.
