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CIDR Calculator

Break down a CIDR block into its addresses.

What Is a CIDR Calculator?

The CIDR Calculator takes a CIDR notation such as 192.168.1.0/24 or 2001:db8::/32 and returns the details of the block: the subnet mask, network address, broadcast address (for IPv4), first and last usable hosts, and the total number of addresses. This free online security tool is useful for CIDR calculator, CIDR subnet calculator, IP range calculator. Common use cases include calculating network blocks, subnet masks, host ranges, broadcast addresses, and IPv4 or IPv6 CIDR ranges. It is designed for quick browser-based analysis and development workflows. Security checks are signals rather than guarantees, so production systems should also be validated against current standards and their specific threat model.

How to Use This CIDR Calculator

  1. 1
    Enter the network informationProvide the IP address, prefix length, or CIDR block.
  2. 2
    Set the prefixChoose the subnet size that matches your network design.
  3. 3
    Calculate the rangeRun the calculator to derive network and host information.
  4. 4
    Review reserved addressesFor IPv4, check network and broadcast addresses and the resulting usable host range.
  5. 5
    Apply the resultUse the calculated ranges for routing, VLANs, firewall rules, or network documentation.

Frequently Asked Questions

Classless Inter-Domain Routing. CIDR notation uses an address followed by a slash and a prefix length to describe a block of IP addresses.
A /24 contains 256 addresses; a /16 contains 65,536. The smaller the number after the slash, the larger the block.
Yes. The tool handles both IPv4 and IPv6 CIDR blocks, showing the network and range for each.

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