IPv4 Equal-Subnet Host Planner

Method, formula and assumptions

Equal child count = 2^(childPrefix - parentPrefix). Addresses per child = 2^(32 - childPrefix). This conventional subnet model reserves network and broadcast addresses, leaving addresses - 2 usable.

Input definitions and supported units

• Parent prefix length: Whole-number count, from 0 to 30; zero is supported where the stated method permits it.
• Child prefix length: Whole-number count, from 1 to 30; must be positive.
• Hosts required per child: Whole-number count, from 0 to 1000000000; zero is supported where the stated method permits it.

Worked example with answer

A /24 split into /27 gives eight children, each with 32 addresses and 30 conventional usable hosts. A 25-host requirement leaves five hosts margin in each child.

How to use the results

This is capacity arithmetic, not an IP address listing. Prefixes /31 and /32 are intentionally excluded because their point-to-point/host semantics differ.

Results retain full precision internally and display up to four decimal places. Very small nonzero results use scientific notation rather than appearing as zero. Check the labels before comparing values across units.

Limitations and references

Cloud providers may reserve more addresses. No routing policy, DHCP range, IPv4 ownership or public-address allocation is inferred.

The method is a self-contained arithmetic, geometric or explicitly stated mathematical model. There are no imported tariffs, empirical presets or equipment specifications; measured values and allowances must come from your own process.

Related planning tools

• IPv6 Site Prefix Capacity Calculator
• Rack Unit Allocation Planner

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