Convert IP Address Ranges to Minimal CIDR Subnets
Transform start and end IPv4 ranges into optimal, minimal CIDR notation blocks for firewalls and routing.
About This Tool
IP Range to CIDR Converter calculates the minimal set of CIDR subnets required to cover an arbitrary IP range, essential for configuring cloud firewalls, AWS Security Groups, and Nginx access lists.
Key Features
Optimal bitwise range-to-CIDR partition algorithm
Generates copyable list of CIDR subnets
Validation against invalid or reversed IP ranges
How to Use This Tool
- Enter the Start IP Address (e.g. 192.168.1.1).
- Enter the End IP Address (e.g. 192.168.1.50).
- Click 'Calculate CIDR Blocks' to view the minimal CIDR subnets list.
Why Use This Tool
- Cloud security groups and firewalls require CIDR notation rather than raw start-end ranges.
- Calculates the exact minimal number of prefixes without overlapping.
Pro Tips
- Paste the resulting CIDR list directly into Cloudflare WAF or AWS Security Group inbound rules
Frequently Asked Questions
Why does an IP range convert into multiple CIDR blocks?
Because CIDR blocks must align with powers of 2 (e.g., /32, /31, /30). Arbitrary ranges like 1-50 cannot be represented by a single power-of-2 subnet.
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