IP Subnet Calculator

By the FastFreeTools Editorial Team · Last reviewed: May 2026 · See our Editorial Policy for methodology, sourcing, and disclaimers.

Calculate subnet details from any IPv4 address and CIDR prefix. Network, broadcast, mask, and host range.

About this tool

IP subnetting divides a network into smaller segments for efficient address allocation. Our calculator takes any IPv4 address with CIDR notation and computes network address, broadcast address, subnet mask, first and last usable host addresses, and total usable hosts. Network engineers, sysadmins, and IT students use this for planning network architectures and studying for certifications.

How to use IP Subnet Calculator

Enter an IPv4 address.
Enter the CIDR prefix length.
Click Calculate.
View network details.

Tips & best practices

/24 = 254 hosts, /16 = 65K hosts, /8 = 16M hosts.
Network and broadcast addresses aren't usable.
Private ranges: 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16.
Subnetting improves security and performance.

Common use cases

Planning IP address allocation.
Configuring router and firewall rules.
Studying for network certifications.
Troubleshooting connectivity issues.

Privacy

This tool runs entirely in your browser. We do not upload, store, log, or process your input on any server. Open your browser's DevTools Network tab to verify — there is no outbound request with your data. See our Privacy Policy for details.

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