Supernet Calculator

Find the smallest covering CIDR for an IPv4 start/end range.

Supernet Calculator finds the smallest CIDR block that covers a start and end IPv4 address or multiple child networks. A supernet is a larger address block created by shortening the prefix length, which expands the range covered by a route or policy rule. Supernetting is useful for summarizing routes, simplifying ACLs, and documenting address ownership, but the minimal covering block may include extra addresses outside the original set. The key concept is binary alignment: CIDR ranges start and end on boundaries determined by the prefix length. Use this calculator to understand coverage and summarization, then verify that any included extra addresses are acceptable before applying the result to routing or security controls.