Subnet & VLSM
Calculator

Why Use Our Free Online Subnet Calculator?

Our free online subnet calculator runs entirely in your browser — no data is sent to any server. It supports all CIDR prefixes from /0 to /32 and delivers instant results without page reloads. Network engineers, CCNA students, and IT administrators use it to quickly compute network addresses, broadcast addresses, usable IP ranges, subnet masks, and wildcard masks. The online VLSM calculator helps you allocate IP subnets efficiently by sorting requirements by host count and computing the optimal CIDR block size for each subnet. All results can be exported as CSV for documentation or copied as a Markdown table for sharing with colleagues.

Network Planning Tools for Every Engineer

Whether you are preparing for a CCNA certification exam, designing an enterprise network from scratch, or allocating address space in an AWS VPC or Azure VNet, our online calculators help you get accurate results instantly. The online IPv6 subnet hierarchy planner breaks down parent prefixes from /48 down to /64, showing exactly how many network segments and host addresses each child block provides — essential for modern dual-stack infrastructure.

The overlap detector scans multiple IP ranges to find conflicts and unused gaps before deployment, preventing routing errors in production environments. The CIDR subtraction tool removes allocated blocks from a parent network to reveal remaining free space, while the aggregation feature collapses contiguous ranges into the smallest possible prefix set.

Every online calculation runs entirely inside your browser using pure JavaScript. No IP addresses, network plans, or configuration data are ever transmitted to a server. The online tools are free to use with no registration, no ads, and no limitations. Export your results as CSV or copy them as Markdown tables for documentation, runbooks, and team sharing.