Overview

There are two ways to use ExactCalcs: browse the calculators directly at exactcalcs.com/calculators, or embed one on your own site with an API key. These docs cover the second path — everything a developer needs to integrate the widget or call the API directly.

Get an API key

Sign up at exactcalcs.com/dev — every account starts on the free plan (100 calculator loads/month, no card required). Your API key is shown on that dashboard once you're signed in.

The fastest way to embed one

Drop this on any page. No build step, no API calls to write yourself — the script handles calling /v1/widget/verify and rendering the calculator.

<div data-exactcalcs-widget="bmi" data-api-key="YOUR_API_KEY"></div>
<script src="https://exactcalcs.com/exactcalcs-widget.js" async></script>

See Embedding a calculator for every option (calculator IDs, theming, and what happens if the key or domain doesn't check out).

What's actually documented here

This is the surface a developer calls directly: the widget verify endpoint, the calculators list, domain management, and webhooks. It doesn't cover this app's own dashboard implementation (signup/login, OAuth callbacks, admin routes) — those aren't a public API, just how exactcalcs.com/dev happens to be built.