Subnet Calculator

Calculate IPv4 network ranges, broadcast addresses, subnet masks and usable hosts from CIDR notation. Runs locally in your browser.

How to use Subnet Calculator

Enter an IPv4 address or explicit prefix. Class-based subnetting defaults to /8 for Class A, /16 for Class B and /24 for Class C, with masks through /32. Choose CIDR — advanced for all /0–/32 prefixes and aggregated ranges. This calculator runs in your browser without verification.

Understanding the results

Review the class default, selected mask, network range, broadcast and host counts. Private RFC 1918 blocks are separate from historical address classes. /31 and /32 use special host-count handling. The result describes address ranges, not whether addresses are currently assigned or reachable.