IP Range Calculator
Expand IP ranges into start, end, count, and CIDR blocks.
Runs locally in your browser. Your input is not uploaded or stored. You can verify this in your browser’s network panel.
What does this tool solve?
Enter a start and end IPv4 address to see the original range and the smallest containing CIDR block — useful for firewall rules and allowlists.
Continue with CIDR / Subnet Calculator, User-Agent Parser · CIDR notation and subnet math
What examples should you start with?
An awkward range
192.168.1.10 – 192.168.1.20Original: 11 addresses · Expanded: 192.168.1.0/27 (32 addresses)A tidy range
192.168.1.0 – 192.168.1.255192.168.1.0/24 (one block)How does it work?
The live-aligned result finds the smallest single CIDR block containing both endpoints. The page also shows the exact multi-block decomposition as a LessInAI extension.
All math runs on 32-bit integers in your browser; nothing is looked up or sent anywhere.
What are the edge cases and limits?
- A single address becomes a /32; the whole IPv4 space becomes 0.0.0.0/0.
- Reversed ranges (end before start) and malformed addresses are rejected with a clear error.
- IPv6 ranges are not supported by this calculator.
Technical reference
Related tools
- CIDR / Subnet CalculatorCalculate network range, broadcast, and host counts from CIDR notation.
- User-Agent ParserParse a User-Agent string into browser, OS, and device details.