Subnet Calculator Tool
Enter any IPv4 address and CIDR prefix to calculate network details instantly.
Subnetting can feel intimidating when you first see slash notation like /27 or /19, but it becomes simple once you break it down. This IPv4 subnet calculator helps you go from an IP + prefix to practical answers: network ID, broadcast, usable range, host count, and more.
What is IPv4 subnetting?
IPv4 subnetting is the process of splitting a larger IP network into smaller logical networks (subnets). Instead of one giant flat network, subnetting creates manageable segments for security, performance, and easier administration.
Every IPv4 address has 32 bits. A subnet prefix (like /24) tells you how many bits represent the network portion. The remaining bits represent host addresses inside that subnet.
Why subnetting matters
- Traffic control: Smaller broadcast domains reduce unnecessary network chatter.
- Security boundaries: You can separate user, server, guest, and management networks.
- Efficient allocation: Right-size subnets to avoid wasting address space.
- Better troubleshooting: Clear structure makes routing and diagnostics easier.
How this ipv4 subnet calculator works
The calculator converts your IPv4 address into a 32-bit value, builds the subnet mask from your CIDR prefix, and then performs bitwise math:
- Network Address = IP AND Subnet Mask
- Broadcast Address = Network OR Wildcard Mask
- Wildcard Mask = Inverse of Subnet Mask
- Host Range = Between network and broadcast (with /31 and /32 exceptions)
Common CIDR prefixes and sizes
- /24 → 256 total addresses, 254 typical usable hosts
- /25 → 128 total addresses, 126 typical usable hosts
- /26 → 64 total addresses, 62 typical usable hosts
- /27 → 32 total addresses, 30 typical usable hosts
- /28 → 16 total addresses, 14 typical usable hosts
- /30 → 4 total addresses, 2 usable hosts (classic point-to-point)
- /31 → 2 addresses, typically used both on point-to-point links
- /32 → single host route
Practical example
Input: 192.168.10.77/26
A /26 mask means blocks of 64 addresses. In the last octet, ranges are 0-63, 64-127, 128-191, and 192-255. Since 77 falls in 64-127, the network is 192.168.10.64 and the broadcast is 192.168.10.127. Typical usable hosts are 192.168.10.65 through 192.168.10.126.
Frequent subnetting mistakes
- Confusing subnet mask and wildcard mask.
- Assigning the network ID or broadcast address to a device.
- Using oversized subnets “just in case,” leading to poor segmentation.
- Forgetting that /31 and /32 are special cases.
Quick subnetting workflow
- Determine how many hosts you need.
- Select the smallest prefix that supports that count.
- Calculate network, broadcast, and usable range.
- Document gateway, DHCP scope, and reserved addresses.
- Repeat for each VLAN or zone.
Final thoughts
An accurate subnet plan is one of the highest-leverage skills in networking. Use this calculator to speed up design and validation, then keep a consistent addressing standard across your environment for easier growth and maintenance.