Need a suggestion for a calculator plugin

Hello.

I am wondering if anyone could give me some suggestions for a calculator plugin.

Below is what I am looking to do (but obviously with WordPress now):
http://www.sipoolandspa.com/how-to-guides/pool-volume-calculator

I basically I need something that can calculate volume of pool water.

I am using visual composer, if that helps. Although I am pretty sure it would not HAVE to be compatible with visual composer as I would probably be able to just use a shortcode in the text editor form the plugin I find. But perhaps someone knows if there is an addon for visual composer that can do this as well.

Thank you in advance for your help and suggestions.