CIDR / Subnet Calculator

Enter an IP address in CIDR notation to calculate network details, binary breakdown, and subnet splits. Supports IPv4 and IPv6.

Last reviewed: April 2026

Reviewed by Shannon Patterson, software engineer · last updated April 2026

New to this tool? Click here for instructions

Examples: 10.0.0.0/8 - 192.168.1.0/24 - 172.16.0.0/12 - 10.10.10.0/28 - 2001:db8::/32

Divide a subnet into equal smaller subnets. Enter the parent CIDR in the Calculate tab first, then choose how many subnets to create.

Parent CIDR

Split into N subnets

IPv4 Subnet Reference (/8 - /32)

CIDR	Subnet Mask	Wildcard	Hosts	Network Class

Enter an IP address in CIDR notation (e.g., 192.168.1.0/24) and click Calculate.

How to Use the Subnet Calculator

To use the CIDR / Subnet Calculator, enter an IP address in CIDR notation (e.g., 10.0.0.0/8) in the input field and click Calculate. The tool will display network address, broadcast address, subnet mask, wildcard mask, first and last usable host, total host count, and a binary breakdown of the IP and mask.

When to Use the Tool in Real Workflows

Use the CIDR / Subnet Calculator when you need to plan and manage IP address spaces in your network infrastructure. It's particularly useful for cloud networking, where you need to allocate and divide CIDR blocks for different environments and Availability Zones.

How It Works

The CIDR / Subnet Calculator uses CIDR notation to calculate network details. CIDR notation consists of an IP address and a prefix length, which indicates how many bits belong to the network portion of the address. The tool then calculates the network address, broadcast address, subnet mask, wildcard mask, and other relevant details.

Tips, Edge Cases, or Limitations

The calculator handles both IPv4 and IPv6 CIDR notation. However, it does not support advanced features like subnet mask conversion or subnetting with variable-length subnet masks (VLSM). For more complex network planning, consider using specialized network design tools.

Frequently Asked Questions

CIDR (Classless Inter-Domain Routing) notation represents an IP address and subnet mask in a compact form. It consists of an IP address followed by a slash and a prefix length.

The network address is the first address in a subnet, and the broadcast address is the last address in a subnet. They are reserved and not used for host assignment.

A /24 subnet has 254 usable hosts. This is because the first and last addresses are reserved for the network address and broadcast address, respectively.

Subnetting is used to divide a large network into smaller, more manageable subnets. This helps in reducing broadcast traffic and improving network security.

The wildcard mask is a binary mask that is used to identify the host portion of an IP address. It is the inverse of the subnet mask, with all network bits set to 0 and all host bits set to 1.

Example walk-through

Worked example: step-by-step

Step 1. Enter the IP address and subnet mask into the calculator interface. For example:

IP Address: 192.168.1.0
Subnet Mask: 255.255.255.0

Step 2. Convert the subnet mask to CIDR notation by counting the number of consecutive 1s in its binary form. The mask 255.255.255.0 translates to /24.

Step 3. Calculate the network address by performing a bitwise AND operation between the IP address and subnet mask. For 192.168.1.0 and 255.255.255.0, the result is 192.168.1.0.

Step 4. Determine the broadcast address by setting all host bits to 1. With a /24 subnet, the broadcast address becomes 192.168.1.255.

Step 5. Compute the number of usable hosts using the formula 2^(32 - CIDR prefix) - 2. For /24, this results in 254 usable hosts.

Step 6. Display the results in a structured format. The expected output for the sample input is:

Network Address: 192.168.1.0
Broadcast Address: 192.168.1.255
Usable Hosts: 254
CIDR Notation: /24

This step-by-step process demonstrates how the CIDR/Subnet Calculator transforms input into precise network configuration details.