Put this calculator on your site
Free to use on any site, commercial or not. No signup, no account, no JavaScript to install, and nothing that tracks the people who use it. Copy the snippet and you are done.
Preview
The snippet
<iframe
src="https://poolgallons.com/embed/pool-volume"
title="Pool volume calculator"
width="100%"
height="620"
style="border:1px solid #dcd9d2;border-radius:12px;max-width:640px"
loading="lazy"></iframe>
<p>
<a href="https://poolgallons.com/pool-volume-calculator">Pool volume calculator</a>
by Pool Gallons
</p>Who this is for
Pool service companies, pool supply shops, builders, HOA and property managers, and anyone writing about pool care who would rather not build a calculator. Every chemical dose depends on knowing the gallons, so it is usually the first question a customer has to answer. The maths is the same one running on the pool volume calculator, kept correct here so it stays correct on your page.
The one condition
Keep the credit line under the frame, and keep it visible. That link is the whole price of the calculator. Hiding or removing it is the only thing that is not allowed, and a hidden link would count against your own site as much as this one.
Changing the size
Width is already fluid, so it fills whatever column you put it in. The height is fixed at 620 pixels because a frame cannot measure itself from the outside. That was measured, not guessed: the calculator needs 584 pixels in a narrow phone column and 558 at full width, so 620 clears both with room for a theme that sets larger text. Raise it if you ever see a scrollbar, lower it if there is a gap underneath. There is no resize script to install, on purpose, because a script is one more thing that can break on your site.