Web Tools
CIDR Merge Calculator
Merge overlapping and adjacent CIDR ranges into minimal supernets. Consolidate firewall rules, ACLs, and IP allowlists by combining redundant CIDR blocks. Shows network details including broadcast address, host range, and host count. Runs entirely in your browser — your data never leaves your machine.
cidr network ip subnet merge firewall
Published May 31, 2026
All interactive tools run entirely in your browser. Your data never leaves your device.
How It Works
Enter CIDR ranges (one per line or comma-separated). The calculator identifies overlapping and adjacent ranges, then merges them into the minimum set of CIDR blocks that cover the same address space. Results include detailed network information for each merged range.
Features
- Merge overlapping CIDRs: combines overlapping and adjacent ranges into minimal supernets
- Flexible input: one CIDR per line or comma-separated
- Reduction count: shows how many ranges were eliminated
- Detail table: network address, broadcast, first/last host, host count for each result
- Supernet detection: correctly handles ranges contained within larger blocks
- 5 preset examples: Adjacent /24s, Overlapping Ranges, Firewall Allowlist, Non-Mergeable, Mixed Prefixes
- Private: all computation runs in your browser — no data transmitted
Use Cases
- Consolidating firewall rules and ACLs for cleaner security policies
- Optimizing IP allowlists and blocklists
- Reducing the number of routing table entries
- Simplifying cloud security group rules (AWS, GCP, Azure)
- Network planning and IP address management (IPAM)