Calculate IPv4 subnet details instantly. Enter an IP address and CIDR prefix to get the network address, broadcast address, first/last usable host, subnet mask, wildcard mask, and host counts.
What this IP subnet range calculator does
This tool helps you quickly break down an IPv4 network into the exact values you need for network design and troubleshooting. Instead of manually converting subnet masks or doing binary math by hand, you can type in an address and prefix and get all key results immediately.
- Network address (subnet ID)
- Broadcast address
- First and last usable host IP
- Subnet mask and wildcard mask
- Total and usable host counts
- Classful label and private/public indication
How to use it
Option 1: Enter IP + Prefix separately
Example: IP 10.10.50.200 and prefix 20.
Option 2: Enter CIDR directly in the IP field
Example: 10.10.50.200/20. If you do this, the calculator can read the prefix from the slash notation automatically.
Press Calculate Subnet Range to view the full output.
Understanding each output field
Network address
The base address for the subnet. Devices do not use this as a host address in typical networks.
Broadcast address
The final address in the subnet, used to send traffic to all hosts in that subnet (except in special designs and modern constrained environments).
Usable host range
Usually from network + 1 to broadcast - 1. For /31, both addresses are typically usable in point-to-point links. For /32, it is a single-host route.
Subnet mask and wildcard mask
Subnet mask marks network bits as 1 and host bits as 0. Wildcard mask is the inverse and is common in ACL configurations.
Quick CIDR reference
- /8 → mask 255.0.0.0 (very large network)
- /16 → mask 255.255.0.0
- /24 → mask 255.255.255.0 (common LAN)
- /30 → 4 total IPs, 2 usable hosts
- /31 → 2 total IPs, typically both usable for point-to-point
- /32 → single IP host route
Why subnet calculation matters in real life
Correct subnet planning prevents address exhaustion, routing issues, and accidental overlap between networks. Whether you are setting up VLANs, cloud VPC subnets, firewall rules, or VPN tunnels, accurate CIDR math keeps your environment stable and scalable.
- Plan clean network segmentation
- Reduce broadcast domains
- Create precise firewall and ACL entries
- Avoid overlapping private IP ranges
- Improve troubleshooting speed
Common mistakes to avoid
- Using the wrong prefix length for the expected host count
- Forgetting that network and broadcast are usually not host addresses
- Mixing up subnet mask and wildcard mask
- Assuming all 172.x.x.x addresses are private (only 172.16.0.0–172.31.255.255 are private)
- Not reserving headroom for future growth
FAQ
Does this calculator support IPv6?
This version is focused on IPv4 subnet range calculations only.
What is VLSM?
VLSM (Variable Length Subnet Masking) means using different prefix lengths in different parts of your network to allocate IP space efficiently.
Is /31 valid for hosts?
Yes, in point-to-point links /31 is widely used and both addresses are typically considered usable.
Final thoughts
A reliable subnet range calculator saves time and reduces mistakes. Keep this page handy whenever you design, audit, or troubleshoot an IPv4 network.