slashwhat — Visual Subnet Calculator & CIDR Planner
slashwhat is a free, browser-based visual subnet calculator for network engineers. Enter any CIDR block (like 10.0.0.0/8 or 192.168.0.0/16) and interactively split and join subnets in a color-coded table.
Features include: IPv4 and IPv6 support, VLAN macro language, multiple color themes, undo/redo, save/load configurations, CSV export, binary visualization, and RFC classification.
No signup required. No backend. Everything runs in your browser. Enable JavaScript to use the calculator.
slashwhat — Visual Subnet Calculator