Enter network block inputs
Use either CIDR input or a separate prefix. A dotted mask can also derive the prefix automatically.
Example data table
| Example Input | Network | Mask | Usable Hosts | Usable Range | Broadcast |
|---|---|---|---|---|---|
| 192.168.12.34/27 | 192.168.12.32/27 | 255.255.255.224 | 30 | 192.168.12.33 - 192.168.12.62 | 192.168.12.63 |
| 10.20.30.40/22 | 10.20.28.0/22 | 255.255.252.0 | 1,022 | 10.20.28.1 - 10.20.31.254 | 10.20.31.255 |
| 172.16.5.200/30 | 172.16.5.200/30 | 255.255.255.252 | 2 | 172.16.5.201 - 172.16.5.202 | 172.16.5.203 |
Formula used
Core block math
Subnet mask from prefix: mask keeps the first prefix bits as 1 and the remaining host bits as 0.
Wildcard mask: 255.255.255.255 - subnet mask.
Network address: IP address AND subnet mask.
Range and capacity math
Broadcast address: network address OR wildcard mask.
Total addresses: 2^(32 - prefix).
Usable hosts: total - 2 for most blocks, while /31 gives 2 usable endpoints and /32 represents one host.
Subnet split preview
When you enter a child prefix, the parent block is divided into 2^(child prefix - parent prefix) equal child networks. Each child starts after the previous child block size, which equals 2^(32 - child prefix) addresses.
How to use this calculator
1. Enter the base address
Type a standard IPv4 address or paste a CIDR block. The calculator accepts either format and normalizes the input for you.
2. Add mask details
Provide a prefix length, a dotted mask, or both. If both are present, they must describe the same block.
3. Add planning inputs
Optional host counts and child prefixes help you estimate fit, utilization, and future subnet splits from the current block.
4. Review the result section
After submission, the result appears below the header and above the form so you can compare outputs without scrolling deep.
5. Inspect advanced details
Check the binary view, integer ranges, address type, and the capacity graph to confirm the block behaves as expected.
6. Export your work
Use the CSV or PDF buttons after calculating a block to save the summary and any displayed child subnet preview.
Frequently asked questions
1. What does a network block calculator show?
It converts an IPv4 address and mask into the network address, broadcast address, host range, address capacity, and subnetting details used for planning and validation.
2. Why are usable hosts lower than total addresses?
Most IPv4 networks reserve one address for the network identifier and one for broadcast traffic, so the count available for hosts is usually total minus two.
3. What is the wildcard mask used for?
A wildcard mask is the inverse of the subnet mask. It is commonly used in ACLs, routing filters, and quick range recognition tasks.
4. Can this calculator handle /31 and /32 blocks?
Yes. It treats /31 as a two-endpoint point-to-point block and /32 as a single-host route, which are both valid edge cases.
5. How does the child subnet preview work?
When you enter a more specific child prefix, the tool divides the parent block into equal child blocks and lists the first results you choose to preview.
6. Why would I enter planned hosts?
Planned hosts let you compare demand with usable capacity, estimate utilization, and see a recommended block size that better fits the requirement.
7. Does entering both prefix and mask improve accuracy?
It improves validation. The calculator checks whether both entries match, which helps catch mistyped masks or incorrect prefix values before deployment.
8. Can I export the result for documentation?
Yes. After a successful calculation, you can download a CSV for spreadsheet use or a PDF for reports, tickets, and change records.