API

The Numcal API. Coming soon. Join the waitlist.

A programmatic version of the numcal calculator for developers and businesses. Same parser, same date-math correctness, same assumption transparency, accessible over HTTP with JSON in and out.

What you'll get

Multi-country business-day calculations. "What date is 30 business days after Jun 1 in both US and Indian banking calendars?" In a single call.
Custom holiday lists. Upload your company's closure calendar; every API call uses it.
DST-correct time zone math. The same engine that handles the spring-forward day on the web.
Inline assumptions. Every response includes the assumptions that produced the answer, for audit trails and compliance contexts.
Stable, versioned. Pin a version; we never break it.

Plans

Tier	Cost	What's included
Free	$0	1,000 calls / month. Rate limited to 30 requests / minute. Attribution required (a small "Powered by numcal" link in your UI, or a header credit for non-UI integrations).
Pro	Coming later	Higher monthly call ceiling, no attribution requirement, custom holiday calendars, multi-seat team accounts, and an uptime SLA. Pricing to be announced closer to general availability.

The free tier stays free indefinitely. Pro pricing will be published before the closed beta ends. Existing waitlist signups get first access and grandfathered pricing for the first year.

Available now: the MCP server

While the HTTP API is in development, the same parser and evaluator are already published as a Model Context Protocol server. Claude Code, Claude Desktop, Cursor, Continue, and any other MCP-compliant client can hand a natural-language query to numcal and get back a deterministic answer with the full assumption row attached.

Install:

npx -y @numcal/mcp

Or wire it into Claude Desktop's claude_desktop_config.json:

{
  "mcpServers": {
    "numcal": {
      "command": "npx",
      "args": ["-y", "@numcal/mcp"]
    }
  }
}

Free, MIT-licensed, no account required. See the npm page for the full README.

Timeline

The HTTP API enters closed beta once the waitlist hits a meaningful threshold (~200 signups with real use cases). Public availability follows a few months after the web product launches in mid-2026.

Join the waitlist

Email api@numcal.com with a sentence about what you'd build. We read every one.