VLSM Calculator

Variable Length Subnet Masking - allocate subnets efficiently from a network block

Enter the parent network in CIDR notation. Subnets will be carved from this block.
Enter hosts needed per subnet. VLSM sorts largest-first for optimal allocation.

Summary

Allocated Subnets

References: RFC 1878 (Variable Length Subnet Table), RFC 4632 (CIDR). VLSM allocates from largest to smallest for efficiency.