Calculator Inputs
Use any valid IPv4 host address. The calculator normalizes it into the correct network block and returns addressing details instantly.
Example Data Table
These sample rows show how the calculator interprets different IPv4 addresses and prefix lengths.
| Input CIDR | Network | Broadcast | Usable Range | Usable Hosts |
|---|---|---|---|---|
| 192.168.10.14/24 | 192.168.10.0 | 192.168.10.255 | 192.168.10.1 - 192.168.10.254 | 254 |
| 10.20.30.40/27 | 10.20.30.32 | 10.20.30.63 | 10.20.30.33 - 10.20.30.62 | 30 |
| 172.16.5.200/20 | 172.16.0.0 | 172.16.15.255 | 172.16.0.1 - 172.16.15.254 | 4,094 |
Formula Used
This calculator uses standard IPv4 prefix mathematics for network analysis and equal-size subnet planning.
- Subnet mask from prefix: mask = leading 1 bits for the prefix, followed by 0 bits for host space.
- Network address: network = IP address AND subnet mask.
- Wildcard mask: wildcard = inverse of subnet mask.
- Broadcast address: broadcast = network OR wildcard.
- Total addresses: total = 2(32 - prefix).
- Usable hosts: usable = total - 2 for most prefixes, with special handling for /31 and /32.
- Subnet borrowing: borrowed bits = ceil(log2(required subnets)).
- Host sizing: host bits = ceil(log2(required hosts + 2)) for normal subnet sizing.
How to Use This Calculator
- Enter a valid IPv4 address.
- Provide a prefix length, a dotted mask, or both.
- Optionally enter required equal subnets for planning.
- Optionally enter required hosts per subnet.
- Choose how many preview rows to display.
- Press Calculate Prefix Details.
- Review the summary table, planner table, and graph.
- Export the visible results with the CSV or PDF buttons.
FAQs
1) What does an IP prefix represent?
An IP prefix states how many leading bits belong to the network portion. The remaining bits belong to hosts. A larger prefix creates smaller subnets with fewer host addresses.
2) What is the difference between a prefix and a subnet mask?
A prefix is the slash notation, such as /24. A subnet mask is the dotted decimal version, such as 255.255.255.0. Both describe the same network boundary.
3) Why are /31 and /32 shown differently?
These prefixes are special. A /31 is commonly used on point-to-point links, and a /32 represents a single host route. Their usable host behavior is different from traditional subnet assumptions.
4) Can I enter any host address instead of a network address?
Yes. The calculator accepts any valid IPv4 host address and normalizes it into the correct network block by applying the subnet mask mathematically.
5) What does the wildcard mask tell me?
The wildcard mask is the inverse of the subnet mask. It highlights host bits and is often used in ACLs, route filters, and matching logic within network policy definitions.
6) Why can the planner say my request is impossible?
A request becomes impossible when the parent network is too small to satisfy both the needed subnet count and the needed hosts per subnet at the same time.
7) Does this calculator support variable-length subnetting?
This version focuses on equal-size subnet recommendations. It is excellent for prefix analysis and structured splitting, but it does not build full mixed-size VLSM allocation plans.
8) What do the CSV and PDF buttons export?
They export the visible result tables generated after calculation. That includes the primary analysis table and any subnet planner tables currently shown on the page.