IPv4 Subnet Calculator

Calculate network address, broadcast address, host range, and CIDR notation from any IP and subnet mask.

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1. Enter an IPv4 address in dotted-decimal notation (e.g., 10.0.0.1) in the IP address field. 2. Enter the subnet mask in dotted-decimal format (e.g., 255.255.255.0) or select a CIDR prefix length from the dropdown. 3. Review the calculated network address, broadcast address, first and last usable host addresses, and total host count. 4. Examine the binary representation breakdown to understand which bits are network vs. host portions. 5. Use the wildcard mask output for configuring access control lists on routers and firewalls.

About This Tool

The IPv4 Subnet Calculator is an essential tool for network administrators and engineers who need to plan and manage IP address allocations. Enter an IP address with a subnet mask or CIDR prefix length, and instantly see the network address, broadcast address, first and last usable host addresses, total number of hosts, and the wildcard mask.

Subnetting is a fundamental networking skill that allows you to divide a large network into smaller, more manageable segments. This calculator handles all the binary math for you, showing both the results and the underlying binary representations so you can verify and learn from each calculation.

Whether you are designing a new network layout, troubleshooting connectivity issues, or studying for a networking certification like CCNA, this tool provides accurate results with clear explanations of each value.

Frequently Asked Questions

A subnet mask is a 32-bit number that divides an IP address into network and host portions. It uses consecutive 1-bits for the network part and 0-bits for the host part. For example, 255.255.255.0 (or /24) means the first 24 bits identify the network.
CIDR notation uses a slash followed by the number of network bits (e.g., /24), while subnet mask notation writes the full mask (e.g., 255.255.255.0). Both convey the same information - CIDR is simply more compact.
A /24 network has 256 total addresses (2^8), but the first address is the network address and the last is the broadcast address, leaving 254 usable host addresses.
The broadcast address is the last address in a subnet. Packets sent to this address are delivered to all hosts on that network segment. It is calculated by setting all host bits to 1.

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