Write online space calculator for a storage facility website

I require a unit size calculator for our new wordpress website [login to view URL] I have permission from our local association to copy their code (if required) from their one located at [login to view URL] This needs to be in our theme and also has to have the summary page or preferably something similar on the same page. If you have any way to make it look or operate better I am also open to suggestions. For more examples please see [login to view URL] [login to view URL] Please ask questions to ensure that you understand the requirements.