CIDR Calculator

What this result means

CIDR notation combines an IPv4 address with a prefix length. The prefix defines the block boundary and therefore the start, end, and total number of addresses in the range.

Understanding CIDR ranges

CIDR, short for Classless Inter-Domain Routing, expresses an IPv4 address block with a slash prefix such as 192.168.1.0/24. The number after the slash is the number of network bits. A larger prefix leaves fewer host bits and creates a smaller block: /24 contains 256 addresses, while /16 contains 65,536.

The calculator normalizes the entered address to its CIDR block. An address such as 192.168.1.42/24 is inside the same block as 192.168.1.0/24, so the network address is 192.168.1.0 and the end of the block is 192.168.1.255. This block-oriented view is useful for route planning, access rules, and understanding allocation ranges.

A dotted-decimal subnet mask and a CIDR prefix express the same split. For /24, the mask is 255.255.255.0 and the wildcard mask is 0.0.0.255. Total address count includes every address in the block. Traditional usable-host counts normally exclude network and broadcast addresses, while /31 and /32 have special routing semantics.

This V1 calculator supports IPv4 only. It performs its calculation locally and does not query providers or interpret ownership, location, reputation, or reachability. For that context, use the IP Lookup and ASN tools after calculating the relevant block.