Free calculator widgets for WordPress

WordPress takes the widget as it comes, in either editor, and there is nothing to install for it.

Any of the 342 calculators can go on a WordPress page. They are free, carry no ads, follow nobody, need no sign-up and do not expire — and the one on your page stays the current version of the calculator, so a snippet pasted once keeps giving the right answer.

Where it goes in WordPress

Add a Custom HTML block where you want the calculator, and paste. In the classic editor, switch from Visual to Text first. No plugin needed.

The code

This is the whole thing, for the mortgage calculator. The calculator’s own page builds the same three lines for it, pre-filled with whatever you type in first, and every other calculator does the same on its page.

<iframe src="https://www.calculateitnow.dev/embed/mortgage-calculator" title="Mortgage Calculator" width="100%" height="800" style="border:1px solid #e4e1d9;border-radius:12px;max-width:100%" loading="lazy"></iframe>
<p style="font:14px/1.5 system-ui,sans-serif;margin:8px 0 0"><a href="https://www.calculateitnow.dev/mortgage-calculator">Mortgage Calculator</a> by CalculateItNow</p>
<script src="https://www.calculateitnow.dev/embed.js" async></script>

The last line only resizes the frame to fit its contents. Drop it and the widget still works, at the height set on the line above.

What lands on the page

The real calculator, not a picture of one. Try it:

The rest of it

Every widget — all 342 of them, by category, each with its own code.
The one thing we ask — why the credit line sits outside the frame, and why keeping it is what pays for all this.
Somewhere else — the same instruction for the other places people paste it.
For developers — the JSON API, the MCP server and oEmbed, if you would rather not use a frame at all.