Advanced IPv4 Subnet Calculator

Subnet Calculator Form

Use the required fields for direct subnet analysis. Fill the advanced planning fields to model equal-size subnet allocation inside the parent network.

Example Data Table

Input IP	Prefix	Network	Broadcast	Usable Hosts	Example Use
192.168.10.34	/24	192.168.10.0	192.168.10.255	254	Office LAN block
10.20.5.19	/27	10.20.5.0	10.20.5.31	30	Branch VLAN segment
172.16.44.130	/26	172.16.44.128	172.16.44.191	62	Server subnet zone

Formula Used

1) Subnet mask from prefix
Subnet Mask = 2³² − 2^{(32 − Prefix)}

2) Network address
Network = IP Address AND Subnet Mask

3) Wildcard mask
Wildcard = 255.255.255.255 − Subnet Mask

4) Broadcast address
Broadcast = Network + 2^{(32 − Prefix)} − 1

5) Address count
Total Addresses = 2^{(32 − Prefix)}

6) Usable hosts
Usable Hosts = 2^{(32 − Prefix)} − 2
Special cases: /31 supports 2 point-to-point addresses, and /32 represents one host route.

7) Child subnet planning
Possible Child Subnets = 2^{(Child Prefix − Parent Prefix)}
The recommended child prefix is the smallest block size that still satisfies both required subnet count and required hosts per subnet.

How to Use This Calculator

Enter the IPv4 address you want to analyze.
Provide the prefix length, such as 24 for a /24 network.
Optionally enter desired child subnet count and hosts per child subnet.
Set reserved hosts if each child subnet needs dedicated infrastructure addresses.
Click Calculate Subnet to view the result, subnet plan, graph, and export options.

FAQs

1) What does this subnet calculator analyze?

It analyzes an IPv4 address and CIDR prefix, then returns the network address, broadcast address, mask, wildcard, usable range, host count, and related subnet planning values.

2) Does it support /31 and /32 networks?

Yes. The calculator uses special handling for /31 point-to-point links and /32 host routes, instead of forcing the usual “minus two” host rule.

3) How is usable host capacity calculated?

For most prefixes, usable hosts equal total addresses minus the network and broadcast addresses. That becomes 2^(32 − prefix) − 2, except for /31 and /32 cases.

4) Can it help plan equal-size subnets?

Yes. Enter desired child subnets, hosts per child subnet, and reserved hosts. The calculator recommends a child prefix and lists suggested subnet blocks.

5) What is the wildcard mask used for?

A wildcard mask is the inverse of the subnet mask. Network engineers often use it in routing policies, access rules, and match conditions.

6) Why can a subnet plan fail?

A plan fails when the parent network is too small to hold both the requested number of child subnets and the required hosts inside each child subnet.

7) Does private or public classification affect the math?

No. The address scope does not change the subnet math. It simply tells you whether the IP belongs to private, public, multicast, loopback, or reserved space.

8) Why would I export CSV or PDF results?

Exports make it easier to document address plans, attach calculations to design reviews, share subnet tables with teams, and keep deployment records.