Subnet
Calculator
A self-hosted PHP tool for IPv4 & IPv6 subnetting, VLSM planning, overlap checking, and a full REST API.
What's included
Everything for IP planning
IPv4 Calculator
Subnet details, wildcard mask, broadcast address, host range, reverse-DNS zone, binary/hex representation, and route summarisation.
→ read the docsIPv6 Calculator
Full 128-bit arithmetic via GMP. Expanded and compressed forms, binary/hex panel, subnet splitter, ULA generator, and overlap checker.
→ read the docsVLSM Planner
Allocate variable-length subnets from a parent block. Export to CSV, JSON, XLSX, or ASCII. Save and restore named sessions.
→ read the docsREST API
Versioned JSON API for every calculator function. Optional Bearer-token auth, rate limiting, and a machine-readable OpenAPI 3.1 spec.
→ read the docsOverlap Checker
Detect overlapping networks — two CIDRs side-by-side or up to 50 networks at once. Supports both IPv4 and IPv6.
→ read the docsShareable URLs & Embeds
Every result is linkable via a GET-parameter URL. Embed the calculator in any page as a responsive <iframe> with auto-resize.
Allocation Tree
Visualise how subnets nest inside a parent block with gap detection, utilisation summary, and a collapsible tree view.
→ read the docsPHP Client Library
A lightweight PHP wrapper for the REST API. Supports authenticated requests, VLSM sessions, bulk lookups, and PSR-friendly error handling.
→ read the docsOperator Config
All tunable options — API auth, rate limits, Turnstile CAPTCHA, canonical URL, custom branding, and session TTLs — in one place.
→ read the docsInstallation