Embed the Rule of 72 calculator

How long money takes to double at a given rate, or the rate that doubles it in a given time, with the exact figure alongside the estimate. Free to use on any site, with one line of HTML and nothing to sign up for.

Live preview

This is the real widget. Try changing the numbers.

Calculator by smartfin.fyi

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<iframe src="https://smartfin.fyi/embed/rule-of-72.html"
        width="100%" height="910" style="border:0"
        title="Rule of 72 calculator" loading="lazy"></iframe>
<p style="font-size:12px;margin:6px 0 0">Calculator by <a href="https://smartfin.fyi/rule-of-72.html">smartfin.fyi</a></p>

Notes

It fills whatever width you give it, down to phone screens.
It follows your reader's light or dark mode automatically.
It does not track your visitors. No cookies, no analytics, no scripts beyond the calculator itself, so it does not affect anything you have promised your own readers.
A height of 910 suits most layouts. Increase it if your site uses larger text.
The credit line under the widget is optional. Keep it, delete it, or add rel="nofollow" to its link. The widget works the same either way.

Terms: there aren't many. Use it on any site, including commercial ones, at no cost. We may improve the calculator over time, so the embedded version can change. If it ever needs to be retired, this page will say so first.

The full version

The complete rule of 72 calculator on smartfin.fyi has more detail than the embed, including a full breakdown by year.

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