IP Subnet Calculator
Calculate network address, broadcast address, usable host range, subnet mask, and total hosts for any IPv4 address and CIDR prefix. Free online IP subnet calculator with detailed breakdowns and charts.
About This Calculator
The IP Subnet Calculator is a free online tool for network administrators, IT professionals, students, and anyone studying for the CompTIA Network+ exam. It computes all essential IPv4 network properties for any IP address and subnet mask combination, including the network address, broadcast address, usable host range, subnet mask in both decimal and binary notation, wildcard mask, total addresses, and usable hosts.
The calculator uses standard bitwise operations: a logical AND between the IP address and subnet mask produces the network address, and inverting the subnet mask bits gives the wildcard mask. The broadcast address is calculated by setting all host bits to 1. The tool also determines the IP class (A through E) and whether the address is public or private by checking against the reserved private ranges (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16). CIDR notation (Classless Inter-Domain Routing) replaced the older classful system to allow flexible subnet sizing.
Regional Notes
India (IN): Indian ISPs and enterprises commonly use private IP ranges (10.x.x.x, 172.16-31.x.x, 192.168.x.x) for internal networking. IPv4 exhaustion has accelerated IPv6 adoption in India, and the National Internet Exchange of India (NIXI) actively promotes IPv6 deployment. Network engineers in India use the same subnetting principles globally.
United States (US): The US manages the largest block of public IPv4 addresses through ARIN (American Registry for Internet Numbers). US network administrators frequently use CIDR for efficient IP allocation in corporate networks, data centers, and cloud environments (AWS, Azure, GCP all support VPC subnetting with CIDR).
United Kingdom (UK): The UK, through RIPE NCC, follows global IPv4 subnetting standards. British network engineers use CIDR for designing office networks, school LANs, and ISP infrastructure. IPv6 adoption is growing in the UK, but IPv4 subnetting remains fundamental for network configuration and troubleshooting.
Frequently Asked Questions
What is an IP subnet calculator?
An IP subnet calculator is a free online tool that computes network properties for any IPv4 address and subnet mask combination. It calculates the network address, broadcast address, usable host range, subnet mask in binary and decimal, wildcard mask, total number of addresses, and usable hosts. It also determines the IP class (A, B, C, D, or E) and whether the IP is public or private.
How do I use the IP subnet calculator?
Enter an IPv4 address by filling in the four octets (each 0 to 255) and select a subnet mask from the CIDR dropdown menu ranging from /0 to /32. Click Calculate to instantly view all network properties including network address, broadcast address, first and last usable host addresses, total addresses, and usable hosts. The results also include the subnet mask in binary form, wildcard mask, IP class, and IP type.
What is CIDR notation?
CIDR (Classless Inter-Domain Routing) notation represents a subnet mask by appending a forward slash and the number of network bits to an IP address. For example, /24 means the first 24 bits are the network portion (subnet mask 255.255.255.0). CIDR replaced the older classful network system (Class A, B, C) to allow more flexible division of IP address space, enabling network designers to choose any number of network bits from /0 to /32.
How is the network address calculated?
The network address is calculated by performing a bitwise AND operation between the IP address and the subnet mask. For example, with IP 192.168.1.100 and subnet mask 255.255.255.0 (/24), the binary AND of the IP and mask gives the network address 192.168.1.0. This address identifies the network itself and cannot be assigned to any host device.
What is the difference between public and private IP addresses?
Public IP addresses are globally unique and reachable over the internet, while private IP addresses are reserved for internal networks and cannot be routed on the public internet. The private IP ranges are 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16. Private addresses are commonly used in home and office local area networks (LANs) behind a router that performs network address translation.
How many usable hosts does a /24 subnet have?
A /24 subnet has 254 usable host addresses. The total number of addresses in a /24 is 256 (2 to the power of 32 minus 24), but the network address (first address) and broadcast address (last address) are reserved and cannot be assigned to hosts. This leaves 254 addresses available for devices like computers, printers, and phones on the network.
What is the broadcast address?
The broadcast address is the last address in a subnet, used to send data to all devices on that network simultaneously. It is calculated by setting all host bits to 1. For example, in a 192.168.1.0/24 network, the broadcast address is 192.168.1.255. Hosts cannot be assigned the broadcast address; it is reserved for one-to-all communication within the subnet.
What are IP address classes in networking?
IP address classes divide the IPv4 address space into five categories: Class A (0.0.0.0 to 127.255.255.255) for large networks with /8 subnet mask, Class B (128.0.0.0 to 191.255.255.255) for medium networks with /16 mask, Class C (192.0.0.0 to 223.255.255.255) for small networks with /24 mask, Class D (224.0.0.0 to 239.255.255.255) for multicast, and Class E (240.0.0.0 to 255.255.255.255) reserved for experimental use. CIDR has largely replaced classful addressing.