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IP Subnet Calculator
Calculate subnet parameters, view IP address details in binary, and split networks into usable host IP ranges.
About This Tool
Use this IP subnet calculator to quickly compute network details from an IPv4 address and CIDR suffix. Instantly determine network and broadcast IPs, usable host ranges, and binary representations for educational and professional network configuration.
IP Subnetting Logic
Network IP = IP Address AND Subnet MaskSubnetting is computed using bitwise operators on the 32-bit unsigned representation of the IPv4 address. The broadcast address is Network IP OR (NOT Subnet Mask).
How To Use The Output
The network address identifies the subnet itself. The broadcast address is the last address in most IPv4 subnets and is not assigned to a host. The usable range shows the addresses normally available for devices.
CIDR length controls subnet size. A smaller suffix such as /24 leaves more host bits and creates a larger subnet; a larger suffix such as /30 or /31 creates a smaller subnet.
Subnetting Edge Cases
/31 networks are commonly used for point-to-point links, where two endpoints can use both addresses. /32 represents a single host route.
Private IPv4 ranges, NAT, routing policy, and cloud provider rules can affect whether an address is usable in your environment.
Examples
Standard Class C Subnet
IP: 192.168.1.100, CIDR: /24
Result: Network: 192.168.1.0, Broadcast: 192.168.1.255, Usable hosts: 254.
Point-to-Point Link
IP: 10.0.0.1, CIDR: /31
Result: Point-to-point network (RFC 3021) containing exactly 2 usable host addresses.
FAQ
What is CIDR notation?
CIDR (Classless Inter-Domain Routing) represents a subnet mask by the number of leading 1-bits (e.g. /24 corresponds to 255.255.255.0 because it has 24 ones followed by 8 zeros in binary).
Why does a /24 subnet have 254 usable hosts instead of 256?
In a standard subnet, two addresses are reserved: the Network Address (first address, used to identify the network) and the Broadcast Address (last address, used to send traffic to all hosts). Therefore, Usable Hosts = 2^(32-CIDR) - 2.
What is the wildcard mask?
The wildcard mask is the bitwise inverse of the subnet mask (NOT mask). It is frequently used in Router Access Control Lists (ACLs) and OSPF routing configurations.