IP Range to CIDR Block Calculator
Processed in your browser
Convert arbitrary start and end IPv4 address ranges into the minimal set of matching CIDR network subnet blocks.
Range Boundaries
Minimal CIDR Blocks
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Direct In-Browser Handoff
IP Subnetting & Addressing Pipeline
Chain this tool with complementary private browser utilities for a complete zero-server workflow:
Helpful Examples
Small Office Range
192.168.1.100 to 192.168.1.120
Start: 192.168.1.100, End: 192.168.1.120How to Use the IP Range to CIDR Block Calculator
Convert continuous start and end IPv4 ranges into the smallest optimal set of CIDR notation subnets. Perfect for configuring cloud firewall rules (AWS Security Groups, Cloudflare WAF, GCP Firewall) and router routing tables.
Privacy & Data Processing Notice
No user data leaves your browser. Computation is executed entirely on your device. We do not store, view, or transmit your inputs over our network. Your computation remains on your personal machine.
Frequently Asked Questions
Why do some IP ranges require multiple CIDR blocks?
Binary subnets must have host counts that are powers of 2 and aligned on their bit boundaries. Arbitrary IP ranges often span multiple boundary alignments.
Related Utilities
Frequently paired browser tools in Network & Internet Tools