How to add a simple calculator to a web page

Hi all,

To cut a long story short, I have a website, http://poolheaterguide.com, which helps people work out what swimming pool heater is needed. There are calculations for pool area, pool volume and temperature change which are pretty simple but a user input would be great to do the calculations and provide the result.

Is there an easy way to do this without getting buried in code? I am using WYSIWYG Web Builder to rebuild the site and would love to make it more user-friendly.

Cheers, Brian.

http://www.engineeringtoolbox.com/swimming-pool-heating-d_878.html

Thanks for that! Along with a code snippet from mike (body mass calculator) I now have calculators on a majorly revamped site. Not live yet but getting there.