# Subnet & VLAN Calculator

Get the network, broadcast, netmask, and host range from CIDR notation, plus a subnet and VLAN planner.

CIDR math comes up constantly in triage: scoping an alert to a subnet, checking whether a beaconing host shares a /24 with a domain controller, working out how many addresses a firewall rule really covers. It is also easy to be off by one doing it by hand.

## How to read it

Calculate gives the network, broadcast, masks, and host range for an IPv4 or IPv6 block. Add a second address to check whether it is in the same subnet. Special-use ranges, such as RFC 1918 or documentation space, are flagged.

A /31 has no network or broadcast split; RFC 3021 makes it a two-address point-to-point link. A /32 is one host.

Equal split carves a network into same-size subnets. Custom sizes plans subnets largest first for the host counts you give. Supernet finds the smallest block that covers a list.

## Related

- [MAC Analyzer](https://www.cyberkit.win/tools/mac-address/)
- [IP & CIDR Reference](https://www.cyberkit.win/reference/ip-cidr/)
- [Subnetting](https://www.cyberkit.win/drills/ip-cidr/)

Canonical: https://www.cyberkit.win/tools/cidr-calculator/

This runs in the browser. Nothing you enter is uploaded.