What this calculator does:

This VLSM (Variable Length Subnet Mask) calculator takes a base network (IP + CIDR/mask) and splits it into multiple sub-nets of just the right size, based on the number of hosts you need in each one.

How to use:

1. Enter your Base Network IP (e.g. 10.200.0.0) and its CIDR or subnet mask (e.g. /16).
2. Under “Subnets,” for each line give it an optional label and the number of hosts required (minimum 1).
3. Click + Add Subnet to add more entries or the “–” button to remove one.
4. Hit Calculate to generate each subnet’s network address, CIDR, subnet mask, first/last host, broadcast, and usable host count.
5. When you’re happy, use Export CSV to download the full table.