VLSM Calculator

Variable Length Subnet Masking. Give it a base network and your host requirements per subnet — it allocates the most efficient blocks automatically, largest first, zero waste.

Base Network

Prefix Length (of the whole block)

// Subnet Requirements

Name / VLAN

Hosts needed

Address space usage

Allocated Subnets

— — —

Subnet name	Network / Prefix	Subnet mask	Host range	Hosts avail.	Requested

// how VLSM works

VLSM allocates subnets by sorting requirements largest first, then assigning the smallest possible prefix that fits. This avoids wasting large blocks on small requirements.