IP Subnet Calculator

About this calculator

This calculator turns a CIDR prefix (like /24) into full subnet details: the subnet mask (e.g. /24 → 255.255.255.0), the wildcard mask (its bitwise inverse, used in access-control-list rules), the total address count (2 raised to the power of the remaining host bits), and the usable host count, which subtracts two addresses reserved for the network address and the broadcast address. A /24 network, for instance, has 256 total addresses but only 254 usable for hosts.

Network engineers and system administrators use this daily when designing IP address schemes, splitting a larger network into smaller subnets (subnetting) or combining several into one (supernetting/CIDR aggregation), and configuring VLANs and firewall rules; students preparing for certifications like CompTIA Network+ or Cisco's CCNA rely on it to check subnetting practice problems; and cloud engineers use the same math to plan VPC and subnet address ranges. Enter an IP address and CIDR prefix to get the full breakdown.