CIDR & IP Subnet Calculator Guide
Subnetting is the practice of dividing a single physical network into multiple logical subnetworks. This helps optimize network traffic, organize devices, and secure subnets. Our calculator takes an IP address and a subnet mask (or CIDR prefix) and calculates network addresses, host address ranges, broadcast addresses, and wildcard masks.
⚙️ Key Features
- Calculates complete subnet metrics from an IP address and CIDR prefix length (e.g. /24).
- Displays host address ranges, network address, broadcast address, and total usable host count.
- Generates binary representations of the IP and mask to help visualize subnet divisions.
- Interactive subnet splitter to split a network range into smaller subnets.
📖 How to Use
- Enter the base IP address (IPv4 format, e.g. `192.168.1.1`) in the input box.
- Select the subnet mask prefix (e.g., /24 or 255.255.255.0) using the dropdown list.
- Review the calculated network details in the dashboard metrics cards.
- Use the visual binary breakdown below to understand the network and host bit split.
Subnetting calculations are completed client-side using JavaScript. No IP addresses or network details are logged or uploaded.
Frequently Asked Questions (FAQ)
What does CIDR stand for?
CIDR stands for Classless Inter-Domain Routing. It is a method for allocating IP addresses and routing IP packets, replacing the older class-based system (Class A, B, C) with a more flexible prefix-based system (e.g. /24).
Why are the first and last IP addresses in a subnet unusable for hosts?
The first address in a subnet is reserved as the network address (used to identify the subnet itself). The last address is reserved as the broadcast address (used to send packets to all devices on the subnet).
What is a wildcard mask?
A wildcard mask is the bitwise inverse of a subnet mask (calculated by subtracting the subnet mask from 255.255.255.255). It is commonly used in router access control lists (ACLs) to match IP addresses.