What is a VLSM calculator?

A VLSM calculator applies standard IPv4 subnet math (RFC 950 / CIDR) to compute network boundaries, masks, and host counts without manual binary conversion.

How does this tool work?

You enter IPv4 addresses, masks, or CIDR notation. The calculator bitwise-ANDs the address with the mask to find the network ID, then derives broadcast, wildcard, and host ranges.

When should I use a vlsm calculator?

Use it during CCNA study, VPC design, firewall rule documentation, IPAM planning, and troubleshooting when you need quick confirmation of subnet boundaries.

Yes. IP Checker Online runs calculations in your browser with no account required.

Does it support IPv6?

These calculators focus on IPv4. For IPv6 prefix planning, use our IPv6 Test and IP Subnet Calculator IPv6 tab.

What is CIDR notation?

CIDR writes the prefix length after a slash (e.g. /24). It replaces legacy classful networks and is used in routing tables worldwide.

What is a subnet mask?

A subnet mask marks which bits belong to the network portion. A /24 equals 255.255.255.0 with 254 usable hosts in typical subnets.

Can I use private IP ranges?

Yes. RFC 1918 addresses (10.x, 172.16–31.x, 192.168.x) use the same subnet mathematics as public space.

How is broadcast address calculated?

Set all host bits to 1 in the subnet — bitwise OR of network address with the inverted mask.

Variable Length Subnet Masking uses different prefix lengths within one parent network to minimize wasted addresses.

What order are subnets allocated?

Largest host requirement first (standard VLSM practice) to reduce fragmentation.

IP Tools

VLSM Calculator – Variable Length Subnet Mask Calculator

Variable-length subnet mask planning with automatic subnet allocation.

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