Calculate IPv4 subnet details instantly. Enter an IP address and CIDR prefix to get the network address, broadcast address, usable host range, subnet mask, wildcard mask, and more.
192.168.1.0
192.168.1.255
192.168.1.1
192.168.1.254
256
254
255.255.255.0
0.0.0.255
11000000.10101000.00000001.00000000
11111111.11111111.11111111.00000000
Enter an IPv4 address (e.g., 192.168.1.100) in the IP address field and select a CIDR prefix length (e.g., /24) using the dropdown or slider. The calculator instantly computes all subnet details: network address, broadcast address, first and last usable host addresses, total number of hosts, number of usable hosts, subnet mask in dotted-decimal notation, wildcard mask, binary representation of the subnet mask, IP class (A/B/C/D/E), and whether the address is private (RFC 1918) or public. The common subnets reference table shows CIDR notation, subnet masks, and host counts for the most frequently used prefix lengths (/8 through /32).
The IPv4 subnet calculator is essential for network engineers designing and segmenting corporate networks, system administrators configuring routers, firewalls, and DHCP scopes, cloud engineers setting up VPC subnets in AWS, Azure, or GCP, DevOps professionals configuring Docker and Kubernetes network policies, IT students studying for CCNA, CompTIA Network+, or other networking certifications, security professionals defining firewall rules and access control lists, ISP engineers planning IP address allocation, and anyone troubleshooting network connectivity issues by verifying that devices are on the correct subnet.
IPv4 addresses are 32-bit numbers divided into a network portion and host portion by the subnet mask. The CIDR prefix length (/0 to /32) indicates how many bits are used for the network portion. The network address is obtained by ANDing the IP with the subnet mask. The broadcast address is obtained by ORing the IP with the wildcard mask (inverse of subnet mask). Usable hosts = 2^(32-prefix) - 2 (excluding network and broadcast addresses). Private IP ranges defined by RFC 1918 are: 10.0.0.0/8 (Class A), 172.16.0.0/12, and 192.168.0.0/16 (Class C). IP classes: Class A = 1.0.0.0-126.255.255.255 (/8), Class B = 128.0.0.0-191.255.255.255 (/16), Class C = 192.0.0.0-223.255.255.255 (/24), Class D = 224-239 (multicast), Class E = 240-255 (reserved).
CIDR (Classless Inter-Domain Routing) notation expresses an IP address and its subnet mask as IP/prefix, like 192.168.1.0/24. The prefix number (0-32) indicates how many bits of the 32-bit address are the network portion. /24 means 24 network bits and 8 host bits, giving 256 addresses (254 usable).
The network address (all host bits set to 0) identifies the subnet itself and cannot be assigned to a device. The broadcast address (all host bits set to 1) is used to send packets to all devices on the subnet. Neither can be used as a host address, which is why usable hosts = total - 2.
Private IP addresses (RFC 1918) are reserved for internal networks and are not routable on the public internet: 10.0.0.0/8 (10.0.0.0–10.255.255.255), 172.16.0.0/12 (172.16.0.0–172.31.255.255), and 192.168.0.0/16 (192.168.0.0–192.168.255.255). Devices using these addresses access the internet through NAT (Network Address Translation).
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