Free CIDR Calculator Online - TestMu AI (Formerly LambdaTest)

What is a CIDR calculator?

A CIDR calculator is a free online tool that turns CIDR notation, such as 192.168.0.0/24, into the network details engineers need every day. From a single IP address and prefix it works out the network address, the broadcast address, the full IP range, the subnet mask, and the number of total and usable hosts in the block.

Instead of doing binary math by hand, you read the answer in seconds. This makes a CIDR calculator a fast companion when you plan address space, size a subnet, write firewall rules, or carve a cloud network into smaller ranges. It is also a clear way to learn how CIDR and subnetting map to real IPv4 addresses.

What is CIDR notation?

CIDR, short for Classless Inter-Domain Routing, is a compact way to describe a block of IP addresses. It writes an address followed by a slash and a prefix length, such as 192.168.0.0/24. Understanding the parts makes every result from the calculator easy to read:

• The base address: The portion before the slash, like 192.168.0.0, marks the start of the block the prefix describes.
• The prefix length: The number after the slash, the /n, sets how many leading bits are fixed for the network, so /24 fixes the first 24 bits.
• The host portion: The remaining bits identify hosts inside the block, so a /24 leaves 8 host bits and a /16 leaves 16 host bits.
• Block size: A smaller prefix covers more addresses, so a /16 is far larger than a /24, while a larger prefix like /30 covers only a handful of addresses.

How to use the CIDR calculator?

Getting a full breakdown of any CIDR block takes only a few seconds, and nothing is installed or uploaded. Follow these steps:

• Enter the IP address: Type an IPv4 address such as 192.168.0.0 into the IP address field. This is the starting point the calculator uses to work out the network.
• Choose the CIDR prefix: Select a CIDR prefix from /1 to /32 to set how many bits are fixed for the network, for example /24 to describe a 256-address block.
• Calculate the network details: Click Calculate to generate the network and broadcast address, the full IP range, the subnet mask, and the total number of addresses in the block.
• Copy or reuse the results: Copy any value, including the IP range, subnet mask, or hex output, straight into firewall rules, cloud VPC settings, or network documentation.

Features of the CIDR calculator

As a tool, the CIDR calculator offers a few capabilities that make subnet math effortless. Here are the features of our calculator:

• Full Network Breakdown: Every result includes the network and broadcast address, the IP range, the subnet mask, and the total address count in one view.
• CIDR to IP Range: The calculator converts any CIDR block straight into its first and last address, so you see the exact span a prefix covers.
• Multiple Output Formats: Results are shown in dotted decimal, long integer, and hexadecimal, which suits scripts, firewalls, and low level tooling alike.
• Containing CIDR Blocks: For a single host the tool lists the larger CIDR blocks that contain it, which is handy when you trace routes and supernets.
• Browser-Based Calculation: All math runs locally in your browser, so the addresses and prefixes you enter are never uploaded to a server.
• No Signup or Limits: The calculator is free with no login and no cap, so you can work through as many subnets as your plan needs.

Use cases of the CIDR calculator

A CIDR calculator is useful anywhere IP addressing has to be planned, secured, or documented. It speeds up each of these workflows by doing the subnet math for you:

• Network Planning: Size each subnet to its host count so address space is split cleanly without overlap or waste across a campus or data center.
• Firewall and Access Rules: Turn a CIDR block into an exact IP range so allow and deny rules cover the right hosts and nothing more.
• Cloud VPC Subnetting: Carve a VPC range into public and private subnets with the correct masks before you launch resources in the cloud.
• Routing and Supernetting: Check which larger block contains a host, then pair the result with the Decimal to IP and IP to Binary tools to inspect addresses bit by bit.
• Learning and Documentation: Confirm masks and ranges while you study subnetting, and reach for the Binary to IP tool when you convert host bits back into readable addresses.

This calculator is maintained by TestMu AI (formerly LambdaTest), the team behind a unified testing platform, so it is shaped by the same focus on accurate, network-aware tooling that engineers rely on. For related address conversions, the Binary to Hex tool covers another common format need.

Frequently Asked Questions (FAQs)

What is a CIDR calculator?

A CIDR calculator is an online tool that turns CIDR notation such as 192.168.0.0/24 into network details. It returns the network and broadcast addresses, the IP range, the subnet mask, and the count of total and usable hosts in the block.

What does the /24 in CIDR notation mean?

The /24 means the first 24 bits of the address are the network portion and the remaining 8 bits identify hosts. A /24 equals the subnet mask 255.255.255.0 and contains 256 addresses, of which 254 are usable for hosts.

How many IP addresses are in a /24?

A /24 block contains 256 IP addresses in total. Two of these are reserved, the network address and the broadcast address, which leaves 254 usable host addresses. The /24 prefix maps to the subnet mask 255.255.255.0.

How do I calculate usable hosts from a CIDR prefix?

Usable hosts equal 2 raised to the power of 32 minus the prefix, minus 2 for the network and broadcast addresses. For a /26 that is 2 to the power of 6, which is 64 addresses and 62 usable hosts. A /31 and a /32 are special cases.

What is the difference between CIDR and a subnet mask?

They describe the same boundary in different ways. CIDR notation uses a prefix length such as /24, while a subnet mask writes those same network bits as dotted decimal such as 255.255.255.0. The CIDR calculator shows both for every block you enter.

Is the CIDR calculator free?

Yes, the CIDR calculator is completely free with no signup, login, or usage limit. You can calculate as many subnets and IP ranges as you need. The tool is maintained by TestMu AI (formerly LambdaTest).

Does the CIDR calculator support IPv6?

This calculator is built for IPv4 CIDR notation, with prefixes from /1 to /32. IPv6 uses a much larger 128-bit address space and a different prefix range, so IPv4 results from this tool should not be applied to IPv6 networks.

Is my input sent to a server?

No. All calculation happens in your browser and nothing is uploaded. The IP addresses and prefixes you enter never leave your machine, which makes the tool safe to use with internal addressing plans and private network details.