NetCarve — subnet calculator & address planner

Calculates and plans IPv4/IPv6 subnetting entirely on-device: quick calculator, visual planner, VLSM solver and conflict checker.

Plan address space, not just calculate it. Most subnet calculators answer one question: what is this subnet? NetCarve answers the one that actually takes the time — how should this client's address space be laid out, and how do I get that plan into the documentation? Quick calculator (IPv4 and IPv6) Paste anything: 10.20.0.0/16, 192.168.1.37 255.255.255.0, 2001:db8::/48, even fe80::1%eth0. You get the network, mask, wildcard, broadcast, first and last usable address, the counts, and a bit ruler showing exactly where the network bits stop. Reserved ranges — RFC 1918, CGNAT, documentation blocks, link-local, ULA and the rest — are flagged as you type, with deprecated allocations marked as such. Click any value to copy it, or take the whole result as a Markdown table. Drag the prefix slider and every figure retunes as you go. Visual planner Keep named projects. Start from a root block and split it, split it again, or carve it straight down to /24s in one step. Name each subnet, give it a VLAN ID and a colour, and watch the utilisation bar fill. Join a branch back and NetCarve tells you exactly what you would lose first. Undo and redo throughout, and the whole tree is keyboard-driven: arrow keys move, S splits, J joins, F2 renames. IPv6 works the same way, with /64s badged as the standard subnet size. VLSM solver Give it a base network and a list of host counts. It sizes each requirement, allocates from the lowest-addressed block that fits, and shows the waste alongside the leftover free blocks. If a requirement does not fit, it tells you by how many addresses. One click sends the whole solution into the planner as a named plan. Conflict checker Paste a list of blocks — a merger, a site-to-site VPN, an inherited spreadsheet — and see the duplicates and containment chains immediately. Comments and blank lines are ignored; bad lines are named rather than silently dropped. IPv4 and IPv6 are compared separately. Bases and bit mathematics A value shown at once in decimal, hexadecimal, binary and its address form, at a width you choose from 8 to 128 bits — because NOT 0xFF is not the same answer in eight bits as in thirty-two. The bit display is an input: click a bit and every base follows. Alongside it, AND/OR/XOR/AND NOT, NOT and shifts on real addresses, and prefix-to-mask conversion in both directions with the wildcard and the set-bit count. Export that fits your documentation Markdown, plain text, CSV and JSON. The Markdown table drops straight into a client report, plain text goes into a ticket or a terminal, and the JSON is a complete backup you can import again later. Private by design NetCarve asks for two permissions: storage, and context menus. It has no site access, makes no network requests of any kind, and contains no analytics. Every calculation happens in your browser and every project stays in your browser profile. Nothing is ever sent anywhere.