VLSM Subnet Calculator
How VLSM works
VLSM (Variable Length Subnet Masking) splits a network into subnets of different sizes – matching the actual host demand without wasting addresses. The calculator automatically sorts the requirements from large to small and assigns correctly aligned blocks.
- Host demand: Enter the number of hosts needed per subnet. The calculator picks the smallest fitting prefix (including network and broadcast address).
- Order: Largest networks first – this keeps the blocks cleanly aligned.
- Overflow: If the demand does not fit the base network, the tool reports it immediately.