Subnet by Host Count
Enter the number of hosts you need and it calculates the smallest matching subnet prefix, mask, and total address count. All calculations happen inside your browser.
How to use
- Enter the number of hosts (devices) needed.
- Click "Calculate".
- Check the smallest matching prefix, mask, and address count.
Frequently asked questions
Why are usable hosts 2 fewer?
Each subnet cannot use its first address (network) or last address (broadcast) for real devices, so usable hosts is the total addresses minus 2.
How is the prefix chosen?
It calculates the smallest subnet (the largest prefix value) that accommodates all the hosts you entered.
Are the entered values sent to a server?
No. All calculations happen only inside your browser, and the values are never sent to or stored on any server.
Practical example and verification criteria
Subnet by Host Count: Distinguish IPv4 from IPv6 and select exactly the input the page accepts: an address, CIDR prefix, netmask, or start/end range. Each IPv4 octet must be 0–255 and a prefix must fit the address family's bit range. For host counts, first check the rules for including network and broadcast addresses.
Subnet by Host Count: For a quick check, start with 254 hosts → /24 as a small input whose result relationship you can verify directly. Confirm that the input summary, units, and options match your intent before applying the tool to real values or a copy of the source; this reduces setup mistakes.
Subnet by Host Count: Split the address at binary boundaries and verify that the first and last network addresses, membership result, and total address count agree. Feed a conversion result into the reverse tool to see whether the original is recovered. Remember that a calculation does not change router, VLAN, or firewall settings or guarantee the current route.
Subnet by Host Count · Work record: For real work, record the input conditions, selected options, and result together. Do not assume the same state will remain after a refresh or device change. Preserve important results separately using copy, download, a screenshot, or another method the page supports, then reopen them in the target environment.
Subnet by Host Count · Error check: If an error or unexpected result appears, reduce the input, run again with default options, and then change one condition at a time. Recording error messages and boundary values helps distinguish format issues, unsupported cases, and browser resource limits, and prevents an empty result from being mistaken for success.
Subnet by Host Count · Scope of use: Check the page guidance for browser processing versus server lookup, storage location, and supported scope. Use sensitive source material or secrets only when strictly necessary. High-impact work such as legal, financial, or medical decisions or changes to an operational system requires current authoritative information and a separate verification process.