Why this tool is useful
Use this calculator when documenting a routed block, checking whether an address belongs to the expected subnet or planning a point-to-point IPv4 link without exposing infrastructure data to a lookup service.
Developer & Data · runs locally
IPv4 Subnet Calculator
Calculate an IPv4 CIDR network, broadcast address, netmask, wildcard mask, address count and RFC 3021-aware usable host range locally.
Ready. Your working data stays in this browser.
How it works
The browser parses four strict decimal octets, applies the prefix as a 32-bit mask and derives every boundary arithmetically; /31 follows RFC 3021 and /32 is treated as one host route.
Practical example
For 192.0.2.130/26 the network begins at 192.0.2.128, the broadcast address is 192.0.2.191 and the traditional usable range contains 62 hosts.
Validation
The calculation is deterministic and explains validation errors instead of silently changing invalid input.
Privacy boundary
Input and output remain in this tab. Copy and download happen through browser APIs without a server upload.
Result passport
Every run reports its tool mode, timestamp and input/output size so transformed data can be audited.