IP ADDRESS TOOLS
Smallest Covering CIDR
Combine IPv4 or IPv6 addresses and ranges into the smallest single CIDR that covers them all.
Calculated in your browser · No API request
Your addresses
IPv4 / IPv6
Coverage result
Your result will appear here
Enter your addresses to see their covering CIDR, address range, and any extra coverage.
Understand the coverage
The longest possible prefix gives the smallest single covering range. That range can include addresses outside your original entries. Overlapping entries are counted once, and CIDRs with host bits are normalized.
Counts include every address in a range, including network and broadcast addresses. Review additional coverage before using a result in an allowlist or blocklist.
Enter individual addresses or CIDR ranges, with up to 1,000 entries. IPv4 and IPv6 cannot be mixed in one calculation. IPv6 address counts remain exact, even for very large ranges.