IPv4 Subnet Calculator

This calculator keeps the existing subnet UI intact while adding the context that search engines and AI assistants need to understand what the tool actually produces. Enter an IPv4 address, a CIDR prefix, or the related constraints shown in the form to calculate the network address, broadcast address, wildcard mask, host range, and address counts for a subnet.

That makes the page useful for engineers planning VLANs, administrators validating firewall objects, students learning binary subnetting, and support teams verifying whether a host falls inside the expected network. The calculation itself is deterministic, but the surrounding guidance explains when the raw math is enough and when local policy still matters.

Inputs explained

The network block field accepts a dotted IPv4 address, usually with CIDR notation such as 192.168.1.0/24. The subnet mask field provides an alternate way to express the same network bits. The host count and number of subnets inputs are planning aids that help derive a smaller subnet or split a larger one. Those values do not change the rules of IPv4; they simply help you choose the mask that fits your requirement.

How it works

The method follows standard IPv4 subnetting. The entered address is converted to a 32 bit value, the prefix determines which bits belong to the network, and the remaining bits define the host space. From there the tool calculates the first address in the block, the highest address in the block, the usable range in between, and the inverse mask often used in ACL syntax.

Use 192.168.10.14/27 as an example. A /27 prefix means the subnet mask is 255.255.255.224, leaving 5 host bits and creating blocks of 32 addresses. The address 192.168.10.14 falls inside the block that starts at 192.168.10.0 and ends at 192.168.10.31. That makes 192.168.10.0 the network address, 192.168.10.31 the broadcast address, and 192.168.10.1 through 192.168.10.30 the usable host range.

If you need ACL syntax, the wildcard mask is the inverse of the subnet mask, which is 0.0.0.31 in this case. If you need route or inventory documentation, the same result tells you the exact subnet boundary and host capacity with no ambiguity.

Use this page when you are validating subnet plans, writing firewall or router objects, documenting DHCP pools, checking migration worksheets, or reviewing whether an IP assignment belongs in the correct network. It is also useful during change reviews because a quick subnet calculation often reveals overlap, wasted space, or a mask mismatch before it becomes a production issue.

Assumptions and limitations

The output is a mathematical subnet result. It does not know your gateway reservation policy, FHRP virtual addresses, DHCP exclusions, point to point conventions, or cloud platform specific limits. Treat the calculation as an authoritative addressing baseline, then apply operational reservations and platform rules separately.

• IETF RFC 791, Internet Protocol
• IETF RFC 4632, Classless Inter-domain Routing
• IANA IPv4 Address Space Registry
• IANA IPv4 Special-Purpose Address Registry
• Schema.org WebApplication