IP Range to CIDR Converter

Type a start and end IP to get the exact CIDR blocks that cover it — nothing more, nothing less.

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Frequently Asked Questions

CIDR blocks must start on a boundary matching their size, so an arbitrary range is covered by a mix of block sizes.

Yes. Use CIDR list tools and choose Summarize — overlapping and adjacent blocks are merged.

Yes, IPv4 and IPv6 are both supported.

Up to 20,000 list entries and 5,000 output blocks, all computed in your browser.

IP Range to CIDR Converter — Minimal CIDR Blocks - Privacy-First, Offline Developer Tool

Global Architecture: This tool runs entirely in your browser using WebAssembly. Unlike server-side alternatives, your data (JWTs, Logs, SQL) never leaves this device. It works offline and handles massive files (1GB+) bounded only by your RAM.