IPv4 Range Calculator
Tip: If you type CIDR in the IP field (like 10.0.0.15/16), prefix length is detected automatically.
What an IP range calculator does
An IP range calculator takes an IPv4 address and subnet prefix (CIDR) and gives you the exact boundaries of that subnet. Instead of manually doing binary math, you instantly see the network address, broadcast address, first usable host, and last usable host.
This is useful for network design, firewall rules, VLAN planning, cloud security groups, VPN routing, and troubleshooting when one host can reach another but a third one cannot.
How to use this calculator
Step 1: Enter an IP address
Type an IPv4 address such as 172.16.20.44. You can also type CIDR directly, for example 172.16.20.44/20.
Step 2: Enter the CIDR prefix
Add the subnet length (0 to 32). If your IP already includes /xx, the tool will auto-fill the prefix.
Step 3: Calculate
Click Calculate Range to view complete subnet details:
- Network ID
- Broadcast address
- Usable host range
- Subnet mask and wildcard mask
- Total addresses and usable hosts
- Private/public detection and IP class
Understanding the output
Network address
The first address in the subnet. It identifies the subnet itself and is not assigned to a normal host (except special cases).
Broadcast address
The last address in the subnet. In traditional IPv4 LANs, it is used for broadcasting to all hosts in the subnet.
First and last usable host
For most subnets, host assignments start one above the network address and end one below the broadcast address. In /31 and /32 networks, the behavior is special and handled automatically by the calculator.
Common CIDR sizes at a glance
- /24 = 256 total addresses (254 traditionally usable)
- /25 = 128 total addresses (126 traditionally usable)
- /26 = 64 total addresses (62 traditionally usable)
- /27 = 32 total addresses (30 traditionally usable)
- /28 = 16 total addresses (14 traditionally usable)
- /30 = 4 total addresses (2 traditionally usable)
- /31 = 2 addresses (point-to-point use case)
- /32 = single host route
Frequent mistakes this tool helps avoid
- Using the wrong subnet mask and creating overlapping networks
- Accidentally assigning network or broadcast addresses to hosts
- Miscalculating host capacity for VLANs or cloud subnets
- Applying firewall rules to incorrect CIDR blocks
Practical use cases
Network engineers use IP range calculations during site rollouts, server migrations, SD-WAN setup, branch office segmentation, and cloud VPC design. Security teams use ranges to scope ACLs, allow-lists, and micro-segmentation rules. Even home lab users rely on CIDR planning when running virtualized services.
Final thought
If you work with IPv4 even occasionally, a reliable IP range calculator saves time and prevents costly addressing mistakes. Keep this page bookmarked and use it whenever you are planning or validating subnet boundaries.