Subnet Calculator
Calculate subnet details from CIDR notation: network address, broadcast, subnet mask, wildcard, host range, and total usable hosts. Free, 100% in your browser.
Reference
What is subnetting?
Subnetting divides a larger IP network into smaller, more manageable sub-networks (subnets). Each subnet has a network address (first address, identifies the subnet), a broadcast address (last address, reaches all hosts), and usable host addresses (everything in between). Subnetting improves network security, reduces broadcast domains, and optimizes IP address allocation.
CIDR notation explained
CIDR (Classless Inter-Domain Routing) notation combines an IP address with a prefix length: 192.168.1.0/24. The prefix length (0–32) indicates how many bits form the network portion. /24 = 255.255.255.0 = 254 hosts. /16 = 255.255.0.0 = 65,534 hosts. /8 = 255.0.0.0 = 16,777,214 hosts. The wildcard mask is the inverse of the subnet mask — used in ACLs and routing configurations.
Common use cases
Network design — plan IP allocation for offices, data centers, or cloud VPCs. Firewall rules — calculate network ranges for access control lists. Cloud infrastructure — size AWS VPC subnets, Azure VNets, or GCP subnetworks. Troubleshooting — verify if two IPs are on the same subnet. Certifications — practice subnetting for CCNA, CompTIA Network+, or similar exams.
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