Online subnet calculator

Find an IPv4 network and address range.

On your device · No account

Privacy details

Online subnet calculator processes your input in this browser. Inputs and results are excluded from analytics. Recent tools save tool names, visit counts and last-visit times. Saved tools store only their names. Draft saving is optional and stays on this device; delete saved text with the draft controls. Loading text from a URL is optional and contacts that server; its URL and your IP address are visible to the server. An optional “Use in” action keeps a handoff in this tab. The next tool removes it on arrival and ignores it if more than a minute has passed.

Copy link includes the inputs you choose to share in the address. Anyone with that link can reopen them. Files and generated results are excluded. Password and key tools share settings only.

Your input

Options and local file

Open a text file on this device

Optional settings apply only to this tab.

Your result

Reset reloads the tool with its starting values and releases open files and device controls. Saved drafts stay on this device until you delete them.

Links include your inputs and settings. Anyone with the link can see them, so leave out private text. Files and generated results are left out; random draws run again.

Keyboard shortcuts

Updated 2026-09-20

Online subnet calculator explained

Split an IPv4 address and CIDR prefix into its network, netmask and full address range. Counts use exact integer arithmetic, including the entire IPv4 range. Host counts distinguish conventional subnets, point-to-point /31 links and single-host /32 routes.

Next: IPv4 to IPv6 converter

Next: MAC address inspector

A worked example

192.168.1.130/26 belongs to 192.168.1.128/26. Its full range ends at 192.168.1.191, and conventional usable hosts run from .129 through .190.

Before you use the result

IPv4 only. This calculates address boundaries; it does not discover your network, allocate addresses or check reachability. Reserved and private ranges are not excluded from the arithmetic.

Cite this page

Citation style

ToolOctopus. “Online subnet calculator.” Updated 2026-09-20. https://tooloctopus.com/ip-subnet-calculator.

Add an access date if your instructions require one.

Citation formatting uses citeproc-js by Frank Bennett and Citation Style Language styles. Licence and source code.