Subnetcalculator

VLSM Calculator

Variable Length Subnet Masking (VLSM) allows you to create subnets of different sizes within a single network, optimizing IP address utilization and reducing waste by up to 80%.

Optimal Efficiency

Automatically calculates the smallest subnet mask that fits your requirements

Reduce Waste

Minimize IP address waste by creating right-sized subnets

Smart Allocation

Intelligent algorithm allocates largest subnets first

VLSM Calculator

Variable Length Subnet Masking (VLSM) allows you to create subnets of different sizes within a single network, optimizing IP address utilization and reducing waste.

Base Network

Enter the main network you want to subdivide (e.g., 192.168.1.0/24, 10.0.0.0/22)

Subnet Requirements

Add the subnets you need. The calculator will allocate them efficiently, starting with the largest requirements first.

VLSM Tips:

  • • Larger subnets are allocated first for optimal efficiency
  • • Each subnet gets the smallest possible subnet mask that fits your requirements
  • • Host count should be the actual devices you need (network and broadcast addresses are handled automatically)

Press Enter or click to calculate optimal subnet allocation

What is VLSM?

Traditional Subnetting vs VLSM

Traditional Fixed-Length

All subnets are the same size, leading to significant IP address waste when subnet requirements vary.

Example: Using /26 for both 50 hosts and 5 hosts wastes 57 addresses

VLSM Variable-Length

Each subnet gets exactly the right size, maximizing efficiency and minimizing waste.

Example: /26 for 50 hosts, /29 for 5 hosts - optimal utilization

When to Use VLSM

  • Enterprise Networks: Different departments need different subnet sizes
  • Cloud Infrastructure: Optimize IP usage in AWS, Azure, or GCP
  • ISP Networks: Allocate customer subnets efficiently
  • Data Centers: Segment services with varying host requirements

Pro Tip: VLSM Algorithm

Our VLSM calculator uses the industry-standard approach: sort subnet requirements by size (largest first), then allocate each subnet using the smallest possible subnet mask. This ensures optimal address space utilization and prevents fragmentation issues.