Overview

The IP/CIDR calculator is an online tool that calculates network information from an IP address and CIDR notation. It supports both IPv4 and IPv6, and computes subnet mask, network address, usable host count, binary representation, and more.

How to Use

1. Select the protocol (IPv4 / IPv6).
2. Enter an IP address (e.g., 192.168.1.100).
3. Specify the prefix length in CIDR (e.g., 24).
4. Click the Generate button.

Specifications & Glossary

• CIDR (Classless Inter-Domain Routing): A notation that combines an IP address with a subnet prefix length using a slash (e.g., 192.168.1.0/24). It replaces classful addressing (Class A/B/C) and enables flexible IP range allocation.
• Subnet mask: A bitmask that separates the network portion from the host portion. /24 corresponds to 255.255.255.0.
• Network address: The first address in the subnet (all host bits set to 0). Used as the routing destination.
• Broadcast address: The last address in the subnet (all host bits set to 1). Does not exist in IPv6.
• Usable host count: Calculated as 2^(host bits) - 2 (excluding network address and broadcast).
• IPv4 vs IPv6: IPv4 uses 32 bits (4 octets, dot-decimal notation); IPv6 uses 128 bits (8 groups of hex digits, colon-separated).
• Binary representation: Displays the IP address as a bit string so you can visually confirm the boundary between the network and host portions.

Use Cases

• Designing subnets for VPCs or on-premises networks.
• Verifying and validating IP ranges for firewall rules.
• Calculating CIDR blocks for network design on AWS, GCP, or Azure.