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Subnet Calculator

Calculate IPv4 subnets with CIDR notation. Get network address, broadcast, mask, host range, and more. Free.

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Subnet Input

Subnet Cidr Ref

CIDR Subnet Mask Subnet Total Hosts Subnet Usable Hosts

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IP Subnet Calculator

The IP Subnet Calculator is a free online tool for network engineers and IT professionals that computes subnet details from an IP address and subnet mask (or CIDR notation). Enter an IPv4 address with its subnet mask (e.g., 192.168.1.0/24) and the tool instantly shows the network address, broadcast address, usable host range, total number of hosts, wildcard mask, and the binary representation of the subnet mask. This is essential for network design, troubleshooting, and IP address planning.The calculator supports both CIDR notation (/8, /16, /24, /27, etc.) and dotted decimal notation (255.255.255.0, 255.255.255.224, etc.) for maximum flexibility. It handles all standard subnet masks from /1 to /32 and correctly identifies the network class (A, B, C) for classful network reference. The tool also includes a VLSM (Variable Length Subnet Masking) mode that lets you subdivide a network into multiple subnets of different sizes to optimize IP address utilization.Network administrators plan IP address allocation across departments and VLANs. System administrators determine the correct subnet for server placement. Security engineers calculate firewall rules and ACL boundaries. Cloud architects design VPC subnets in AWS, Azure, and GCP. CCNA students practice subnetting exercises and verify their manual calculations. Help desk technicians troubleshoot connectivity issues by identifying subnet mismatches. The visual binary representation helps users understand exactly how the mask separates the network and host portions.IP Subnet Calculator is part of the facilita.tools network toolkit. Available in Portuguese, English, and Spanish, optimized for desktop and mobile.

Frequently Asked Questions

What is subnetting?
Subnetting divides a large network into smaller, more manageable sub-networks (subnets). It improves network performance, security, and IP address management by creating logical groupings of devices.
What does CIDR /24 mean?
CIDR /24 means the first 24 bits of the IP address are the network portion, leaving 8 bits for hosts. This equals subnet mask 255.255.255.0 and provides 254 usable host addresses (256 total minus network and broadcast).
How many usable IPs are in a /24 subnet?
A /24 subnet has 254 usable IP addresses. The total is 256 (2^8), but 2 are reserved: the network address (first IP) and broadcast address (last IP). For a /23, you get 510 usable IPs.