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VLSM Calculator

Enter base network plus host counts. Get smallest fitting subnets, largest first.

NetworkMaskRangeNeed/Fit
192.168.1.0/25255.255.255.128192.168.1.1–192.168.1.126100/126
192.168.1.128/26255.255.255.192192.168.1.129–192.168.1.19050/62
192.168.1.192/28255.255.255.240192.168.1.193–192.168.1.20610/14

How to read the result

Each need gets smallest prefix fitting it, aligned to its size boundary, packed largest-first to minimize waste.

Example

192.168.1.0/24 + [100, 50, 10] → 192.168.1.0/25, 192.168.1.128/26, 192.168.1.192/28

FAQ

Why sort largest first?

Packing big blocks first avoids fragmentation and fits more hosts.

What if it does not fit?

Calculator errors. Drop a requirement or start from a shorter prefix (bigger base).