IP Subnet Calculator

Subnet Details:

How Does This Work?

This IP subnet calculator performs bitwise operations on the addresses you provide to determine the properties of a network.

  • Binary Conversion: The calculator first converts both the IP address and the subnet mask from their decimal dot notation into their 32-bit binary equivalents.
  • Network Address: It performs a bitwise AND operation between the binary IP address and the binary subnet mask. The result is the network address, which identifies the subnet.
  • Broadcast Address: To find the broadcast address, it inverts the subnet mask (a bitwise NOT operation) and then performs a bitwise OR operation with the network address. This identifies the last address in the subnet.
  • Host Range & Count: The usable host addresses are all the addresses between the network and broadcast addresses. The number of hosts is calculated as 2(32 - CIDR) - 2, where the '-2' accounts for the unusable network and broadcast addresses.

The Surprising History of IP Addresses

When the internet was in its infancy in the 1970s, as part of the ARPANET project, its creators needed a way for computers to find each other. The solution was the Internet Protocol (IP). The initial system, now known as IPv4, uses a 32-bit address, which allows for about 4.3 billion unique addresses. At the time, this seemed like an inexhaustible number.

No one could have predicted the explosion of the internet, personal computers, smartphones, and IoT devices. By the 2010s, it became clear that the world was running out of IPv4 addresses. This "address exhaustion" was a major crisis that had been foreseen by engineers for decades. The solution is IPv6, a newer system with a 128-bit address space, providing an astronomical number of addresses (approximately 340 trillion, trillion, trillion). The internet is currently in a long, slow transition from the original IPv4 to the much more spacious IPv6.

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Frequently Asked Questions (FAQ)

Why can't I use the Network or Broadcast address for my devices?

These two addresses are reserved for special purposes. The network address is like the "street name" for the subnet; it identifies the network itself. The broadcast address is like a "loudspeaker" for the street; data sent to it goes to every device on that subnet. All other addresses in between are available for individual hosts (like computers, phones, etc.).

What is a good subnet size for a home network?

Most home networks use a /24 subnet (a subnet mask of 255.255.255.0). This provides 254 usable IP addresses, which is more than enough for a typical household's collection of computers, phones, smart TVs, and other devices.

How are the subnet mask and CIDR value related?

They are two different ways of representing the same thing. The subnet mask uses four octets (e.g., 255.255.255.0), while the CIDR value is a single number representing the number of '1's in the binary version of the subnet mask. For example, 255.255.255.0 in binary is 24 ones followed by 8 zeros, so its CIDR value is /24. This calculator syncs them automatically.