IP Range Subnet Calculator

Example Data Table

Input IP	Prefix	Network Address	First Usable	Last Usable	Broadcast	Usable Hosts
192.168.10.34	/27	192.168.10.32	192.168.10.33	192.168.10.62	192.168.10.63	30
10.24.7.200	/20	10.24.0.0	10.24.0.1	10.24.15.254	10.24.15.255	4094
172.16.5.9	/30	172.16.5.8	172.16.5.9	172.16.5.10	172.16.5.11	2
203.0.113.140	/26	203.0.113.128	203.0.113.129	203.0.113.190	203.0.113.191	62

Formula Used

This calculator applies standard IPv4 subnet mathematics to derive network boundaries, host counts, and planning recommendations.

Total addresses = 2^{(32 - prefix)}
Usable hosts = Total addresses - 2, except /31 and /32
Network address = IP address AND subnet mask
Broadcast address = Network address + Total addresses - 1
Wildcard mask = 255.255.255.255 - Subnet mask
Borrowed bits = ceil(log₂(desired subnets))
Child subnet prefix = Parent prefix + Borrowed bits
Host sizing finds the largest prefix that still supports the requested usable hosts and reserved addresses.

How to Use This Calculator

Enter a valid IPv4 address in dotted decimal format.
Provide the CIDR prefix length from 0 to 32.
Add desired subnet count if you want block splitting guidance.
Add required hosts and reserved hosts for capacity planning.
Choose how many child subnet rows you want previewed.
Press Calculate Subnet to show results above the form.
Review network address, mask, broadcast, usable range, and planning outcome.
Use the CSV or PDF buttons to download the calculated output.

Frequently Asked Questions

1. What does CIDR mean in subnetting?

CIDR stands for Classless Inter-Domain Routing. It uses a prefix length such as /24 to show how many bits belong to the network portion of an IPv4 address.

2. What is the difference between total addresses and usable hosts?

Total addresses include every address in the subnet. Usable hosts exclude the network and broadcast addresses in standard IPv4 subnets, except special /31 and /32 cases.

3. Why does a /24 subnet show 254 usable hosts?

A /24 contains 256 total addresses. Two are normally reserved for the network identifier and broadcast address, leaving 254 usable host addresses.

4. What is a wildcard mask used for?

A wildcard mask is the inverse of the subnet mask. It is commonly used in access control lists, routing filters, and rule matching on many network devices.

5. Can this calculator handle private and public IPv4 addresses?

Yes. It calculates the subnet math for any valid IPv4 address and also labels whether the input address belongs to a private, public, multicast, or reserved range.

6. Why would subnet and host goals conflict?

Conflicts appear when you ask for many subnets and many hosts at the same time inside one parent block. Smaller child subnets increase count but reduce available host capacity.

7. Does the calculator support IPv6?

No. This file is designed for IPv4 subnet calculations only. IPv6 uses a different addressing structure and would require its own dedicated logic and interface.

8. When should I export the results?

Export results when you need audit trails, implementation notes, design approvals, client documentation, or troubleshooting records for infrastructure planning and support work.