Introduction
This free IP address calculator helps you find subnet details for both IPv4 and IPv6 addresses. Enter an IP address and subnet mask or CIDR prefix, and the tool will instantly show you the network address, broadcast address, usable host range, wildcard mask, and more. It also displays a visual binary breakdown so you can see exactly which bits belong to the network and which belong to the host.
Beyond basic subnet calculation, you can use the Subnet Splitter to divide a network into smaller subnets and the IP Range to CIDR converter to turn any range of IP addresses into the smallest set of CIDR blocks. Whether you are a student learning how subnetting works or a network engineer planning an address scheme, this tool gives you quick and accurate results without any manual math.
How to Use Our IP Address Calculator
Enter an IP address and subnet details to get full network information, including network address, broadcast address, usable host range, binary breakdown, and more.
Input Mode: Choose "Standard Input" to type an IP address and pick a subnet mask from a list. Choose "CIDR Input" to type the IP and prefix length together, like 192.168.1.0/24.
IPv4 Address: Type a valid IPv4 address using four numbers separated by dots, such as 192.168.1.1. Each number must be between 0 and 255.
Network Class: Pick a class (A, B, or C) to filter the subnet mask list to only show masks that fit that class. Select "Any" to see all options.
Subnet Mask: Pick a subnet mask from the dropdown. This tells the calculator how to split the address into network and host parts. For more focused subnet work, you can also try our dedicated Subnet Calculator.
CIDR Notation: If you chose CIDR Input mode, type the IP address followed by a slash and a prefix length between 0 and 32, such as 10.0.0.0/8. If you need to work exclusively with CIDR blocks, our CIDR Calculator is another helpful option.
Subnet Splitter – Parent Network: Type a network in CIDR format, like 192.168.1.0/24. This is the larger network you want to divide into smaller subnets.
Subnet Splitter – Split By: Choose whether to split by a set number of subnets or by a new prefix length. Then enter the number of subnets you need or pick the new prefix from the dropdown. For more complex variable-length subnetting scenarios, consider using our VLSM Calculator.
IP Range to CIDR – Start and End IP: Type a start IP address and an end IP address. The calculator will find the smallest set of CIDR blocks that cover every address in that range.
IPv6 Address: Switch to the IPv6 tab and type a valid IPv6 address. You can use the short form with double colons, such as 2001:db8::1.
IPv6 Prefix Length: Pick a prefix length from the dropdown. A /64 is the most common size for a single network. The calculator will show the full address, network address, IP range, and total address count.
What Is an IP Address?
An IP address is a set of numbers that identifies a device on a network. Think of it like a home address, but for computers. Every phone, laptop, and server needs one to send and receive data over the internet or a local network. The amount of data those devices exchange depends on the available bandwidth, which determines how fast information can travel between them.
IPv4 vs. IPv6
There are two types of IP addresses. IPv4 uses four groups of numbers separated by dots, like 192.168.1.1. It supports about 4.3 billion addresses. Because the internet grew so fast, that was not enough. IPv6 was created to fix this. It uses eight groups of hexadecimal numbers separated by colons, like 2001:db8::1. IPv6 supports a nearly unlimited number of addresses. If you need to work with the hexadecimal values used in IPv6, our Hex Calculator can help with conversions and arithmetic.
What Is a Subnet?
A subnet is a smaller network inside a larger one. Subnetting splits a big block of IP addresses into smaller, more organized groups. This helps network administrators control traffic, improve security, and use addresses more efficiently. Our Subnet Calculator is specifically designed to handle these breakdowns quickly.
Subnet Masks and CIDR Notation
A subnet mask tells a device which part of an IP address is the network and which part is the host (the individual device). For example, a mask of 255.255.255.0 means the first three groups identify the network and the last group identifies the host.
CIDR notation is a shorthand way to write this. Instead of writing the full mask, you add a slash and a number after the IP address, like 192.168.1.0/24. The number after the slash tells you how many bits belong to the network. For dedicated CIDR block analysis, you can use our CIDR Calculator.
Key Terms
- Network Address – The first address in a subnet. It identifies the network itself and cannot be assigned to a device.
- Broadcast Address – The last address in a subnet. It is used to send a message to every device on that network.
- Usable Hosts – The addresses between the network and broadcast addresses. These are the ones you can actually assign to devices.
- Wildcard Mask – The opposite of a subnet mask. It is used in router configurations and access control lists to define address ranges.
- Prefix Length – The number after the slash in CIDR notation. A longer prefix means a smaller subnet with fewer hosts.
- Binary Representation – IP addresses are ultimately stored as binary numbers. Our Binary Calculator can help you perform conversions and calculations in base-2.
Why Subnetting Matters
Without subnetting, a large network would be slow and hard to manage. Breaking it into subnets keeps traffic organized, limits the spread of broadcast messages, and makes it easier to apply security rules. Whether you manage a home network or a data center, understanding subnets helps you plan your IP address space correctly. When you need to allocate different-sized subnets efficiently, a VLSM Calculator lets you assign variable-length prefixes to match each segment's requirements. And if you want to estimate how long a large file transfer will take across your network, our Download Time Calculator can give you a quick answer based on your connection speed.