Free Online IPv4 Subnet & CIDR Calculator
Subnetting splits large IPv4 networks into smaller, efficient network segments to improve network security and optimize routing bandwidth.
Our free IP Subnet Calculator provides instant calculations for Network Addresses, Subnet Masks, Broadcast Addresses, and Usable Host ranges across all CIDR notation prefixes (/0 to /32).
Key Features of Our Online IP Subnet Calculator
Full CIDR Prefix Support
Calculates subnet bounds across all prefix ranges from /0 up to /32.
Network & Broadcast Calculations
Determines precise starting network addresses and ending broadcast addresses.
Usable Host Capacity
Calculates exact usable IP host assignments for routing configuration.
IP Class Detection
Automatically identifies legacy IP address classes (Class A, B, C, D, E).
How to Use the IP Subnet Calculator
- Enter any valid IPv4 address into the IP Address field.
- Select your target CIDR prefix notation (e.g. /24) from the dropdown list.
- Click "Calculate Subnet" to generate the network parameters.
- Review usable IP host ranges, subnet mask octets, and broadcast values in the breakdown cards.
Frequently Asked Questions (FAQs)
What is a CIDR notation?
CIDR (Classless Inter-Domain Routing) notation specifies the number of leading 1-bits in a subnet mask, written as a slash followed by the number (e.g. /24).
Why are two IP addresses reserved in a subnet?
The first address represents the Network ID and the final address serves as the Broadcast ID, making them unavailable for assignment to host devices.