CIDR Calculator

Calculate CIDR notation, subnet masks, network ranges, and usable hosts for IPv4 addresses with this comprehensive online calculator.

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About This Tool

This CIDR Calculator is a powerful online tool for network administrators and IT professionals to calculate subnet information for IPv4 addresses. Enter an IP address with subnet mask or CIDR notation to instantly calculate the network address, broadcast address, usable host range, subnet mask in decimal and binary formats, network class, and total number of hosts. The tool supports all standard subnet masks from /1 to /32 and provides detailed breakdowns of network calculations. Perfect for planning network infrastructure, troubleshooting connectivity issues, or learning about IP subnetting.

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How to Use

Enter an IPv4 address in the first field (e.g.,
Enter a subnet mask (e.g.,
OR select a CIDR notation (e.g., /
Click 'Calculate CIDR' to see detailed subnet information
View results including network address, broadcast address, usable host range, and subnet details
Use the 'Calculate Subnet' option to explore different subnetting scenarios

Frequently Asked Questions

Find Quick Answers

What is CIDR notation?

CIDR (Classless Inter-Domain Routing) notation is a compact representation of an IP address and its associated routing prefix. It's written as an IP address followed by a slash and a number (e.g., 192.168.1.0/24), where the number indicates the number of bits in the subnet mask.

How do I calculate the number of usable hosts?

The number of usable hosts is calculated as 2^(32 - CIDR) - 2. For example, a /24 subnet (255.255.255.0) has 2^(32-24) - 2 = 256 - 2 = 254 usable hosts. The subtraction of 2 accounts for the network address and broadcast address which cannot be assigned to hosts.

What's the difference between network address and broadcast address?

The network address is the first address in a subnet and identifies the network itself. The broadcast address is the last address in a subnet and is used to send data to all devices on that network. Neither can be assigned to individual hosts.

Can I use this calculator for IPv6 addresses?

No, this calculator is specifically designed for IPv4 addresses. IPv6 uses a different addressing scheme and CIDR notation works differently with 128-bit addresses instead of 32-bit addresses.

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