What is a /24 subnet?

A /24 subnet has a prefix length of 24 bits, giving a subnet mask of 255.255.255.0. It contains 256 addresses (2^8), of which 254 are usable for hosts (the network address and broadcast address are reserved). This is one of the most common subnet sizes for small office and home networks.

How do I find the network address from an IP and CIDR?

To find the network address, perform a bitwise AND between the 32-bit IP address and the subnet mask. The subnet mask is a 32-bit number with the first n bits set to 1 (where n is the CIDR prefix length) and the remaining bits set to 0. For example, 192.168.1.100/24 ANDed with 255.255.255.0 gives a network address of 192.168.1.0.

What is the difference between network address and broadcast address?

The network address is the first address in a subnet and identifies the subnet itself; it cannot be assigned to a host. The broadcast address is the last address in a subnet and is used to send packets to all hosts simultaneously; it also cannot be assigned to a host. The usable host addresses are all addresses between these two, inclusive of the first and last host but exclusive of the network and broadcast.

IP Subnet Calculator (CIDR)

This IP subnet calculator computes all the key details of an IPv4 subnet from an IP address and CIDR prefix length. You enter an IP address in dotted-decimal notation and a prefix length between 0 and 32 after the slash, and the calculator returns the network address, broadcast address, first usable host, last usable host, the total number of addresses in the subnet, the number of usable host addresses, and the subnet mask in dotted-decimal form. Subnetting is the process of dividing an IP address space into smaller logical networks. The CIDR (Classless Inter-Domain Routing) notation describes both the IP address and the size of the network in a compact form such as 192.168.1.0/24. The prefix length tells you how many bits of the 32-bit IP address are fixed for the network portion; the remaining bits identify hosts within that network. A /24 network has 8 host bits, giving 256 total addresses and 254 usable hosts. A /16 has 16 host bits and 65,534 usable hosts. The network address is found by performing a bitwise AND between the IP address and the subnet mask. The broadcast address is found by performing a bitwise OR between the network address and the inverted mask (host mask). The tool is designed for network engineers configuring routers and firewalls, system administrators planning IP address allocations, students studying for networking certifications, and developers building network-aware applications. IPv6 is not supported by this calculator.

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IP address

CIDR prefix length (0-32)

254

usable hosts

Network192.168.1.0

Broadcast192.168.1.255

First host192.168.1.1

Last host192.168.1.254

Subnet mask255.255.255.0

Total addresses256

How it works

The calculator converts the IP address to a 32-bit integer by shifting each octet. The subnet mask is computed as a 32-bit integer with the top prefix bits set to 1 and remaining bits set to 0: mask = 0xFFFFFFFF << (32 - prefix) & 0xFFFFFFFF. The network address is: IP AND mask. The broadcast address is: network OR (NOT mask & 0xFFFFFFFF), which is equivalent to setting all host bits to 1. The first usable host is network + 1 and the last is broadcast - 1. Usable hosts = 2^(32 - prefix) - 2, except for /31 and /32 which are treated as point-to-point and single-host addresses. Each 32-bit result is converted back to dotted-decimal by extracting each byte.

Worked example

IP 192.168.1.0 with prefix /24: mask = 255.255.255.0. Network = 192.168.1.0 AND 255.255.255.0 = 192.168.1.0. Broadcast = 192.168.1.0 OR 0.0.0.255 = 192.168.1.255. First host = 192.168.1.1, last host = 192.168.1.254. Usable hosts = 256 - 2 = 254. These match the default values pre-filled in the calculator above.

Related calculators

Binary Hex Octal Decimal Converter: view IP addresses and masks in binary and hexadecimal.
Numeral System Converter: convert between decimal, binary, octal and hexadecimal.
Data Storage Converter: convert bits, bytes and larger data units for network planning.
Percent Error Calculator: compare estimated and actual host counts for subnet planning.

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