IPv4 Subnet Calculator
Enter an IPv4 address and CIDR prefix to instantly calculate network details.
What Is a Subnet IP Calculator?
A subnet IP calculator helps you split IP networks into logical segments. Instead of manually doing binary math, the calculator takes an IP address and prefix (like /24) and gives you important values such as network address, broadcast address, host range, and subnet mask.
This is useful for network engineers, system administrators, developers, students, and anyone managing routers, VLANs, cloud VPCs, or firewall rules. Even in small offices, proper subnetting improves performance, security, and troubleshooting speed.
How to Use This Calculator
- Enter an IPv4 address (for example, 10.0.5.22).
- Enter the CIDR prefix (for example, 16 for /16).
- Click Calculate Subnet.
- Review the generated network details instantly.
Tip: You can also enter the address in combined format like 192.168.1.10/24. If the prefix field is empty, the calculator will read the prefix from that format automatically.
Understanding the Output
Network Address
The network address is the first address in the subnet and identifies the subnet itself. It cannot be assigned to a regular host device.
Subnet Mask and Wildcard Mask
The subnet mask (like 255.255.255.0) shows which bits represent the network. The wildcard mask is the inverse, commonly used in ACL and filtering rules.
Broadcast Address
This is the last address in a subnet and is used to send packets to all devices in that subnet.
Usable Host Range
For most networks, the first and last addresses are reserved (network and broadcast), so usable hosts are between those two. Special cases:
- /31: two usable addresses (common for point-to-point links).
- /32: a single host route.
Popular CIDR Blocks (Quick Reference)
- /24 → 256 total addresses, 254 usable
- /25 → 128 total addresses, 126 usable
- /26 → 64 total addresses, 62 usable
- /27 → 32 total addresses, 30 usable
- /28 → 16 total addresses, 14 usable
- /29 → 8 total addresses, 6 usable
- /30 → 4 total addresses, 2 usable
Example: 192.168.50.77/26
A /26 subnet has 64 addresses per block. For this IP, the network is 192.168.50.64 and the broadcast is 192.168.50.127. Usable hosts run from 192.168.50.65 to 192.168.50.126, giving 62 usable hosts.
Common Subnetting Mistakes
- Mixing up CIDR notation and subnet mask notation.
- Assigning the network or broadcast address to a host.
- Creating overlapping subnet ranges in the same environment.
- Forgetting that cloud providers may reserve additional addresses per subnet.
Final Thoughts
Subnetting is a core networking skill. A good calculator saves time and reduces mistakes, especially during planning and incident response. Use this tool whenever you need accurate subnet details fast.