Free IP Subnet Calculator
Enter an IP and CIDR to instantly compute the network address, broadcast address, usable hosts and subnet mask. A must-have for network config and firewall planning โ fully local.
Key Features
Core Fields
Network address, broadcast address and usable host range, computed in one step.
Mask Conversion
CIDR prefix length and dotted-decimal mask convert between each other automatically.
Host Capacity
Shows the maximum usable hosts in the subnet for easy capacity planning.
Local Computation
All calculations run in your browser โ no network needed.
How to Use
Enter an IP
Type an IP address and CIDR, e.g. 192.168.1.100/24.
Auto Calculation
Network address, broadcast, mask and host count are displayed automatically.
Copy the Result
Copy all subnet information with one click.
Frequently Asked Questions
What is CIDR?
CIDR (Classless Inter-Domain Routing) represents a subnet with a slash and a number. For example, /24 means the first 24 bits are the network part, corresponding to a 255.255.255.0 mask.
Why is the usable host count reduced by 2?
Each subnet's network address and broadcast address cannot be assigned to hosts, so usable hosts = 2^(32-prefix) - 2.
Is IPv6 supported?
Currently focused on IPv4. IPv6 uses a different address structure and is not yet supported.
Is the calculation accurate?
It is based on standard bitwise operations and matches tools like the Cisco subnet calculator, so it is safe to use for network planning.