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Subnet Calculator

Server-sideProcessed server-side

This tool uses a server-side service for processing; uploaded files or requests are not kept for long-term storage.

About

Paste an IPv4 or IPv6 address with a CIDR prefix (e.g., 192.168.1.10/24 or 2001:db8::1/64) and get the network address, broadcast, first and last usable host, netmask, and total address count. IPv6 skips broadcast (the protocol doesn't have one) and shows the range size instead.

The practical cases where you actually reach for this tool: sizing a VPC or VLAN before clicking create in a cloud console; expanding a vendor-supplied CIDR allowlist into a readable range so you can confirm it covers the IPs you expect; sanity-checking firewall rules where someone wrote /26 and you need to know whether that's 32, 64, or 128 addresses; splitting a /24 into smaller subnets for a branch-office plan.

Everything here is arithmetic — no packets, no scanning, no external lookup. You can paste a private RFC 1918 range or a production address without worrying about it being logged or probed.

How it works

  1. 1Open Subnet Calculator and choose your file or enter the required input.
  2. 2Check the settings and start the process.
  3. 3The tool creates the result with temporary server-side processing.
  4. 4Download the output or copy the result when it is ready.

FAQ

›Which formats are supported?
IPv4 and IPv6 with CIDR, e.g., 10.0.0.5/16 or 2001:db8::/48.
›What about broadcast?
Shown for IPv4. IPv6 has no broadcast; we show first/last addresses instead.
›Can I see usable hosts?
We show first/last and total addresses; subtract network/broadcast as needed for IPv4.
›Is any data stored?
No. The calculation runs per request; nothing is persisted.
›Why CIDR is required?
Prefix length defines the subnet; without it, network boundaries can’t be derived.