How do I make saving calculator like this?

Can some please help me with开发者_Python百科 making a similar saving calculator just like this one at the bottom right corner of this page http://www.clickitrealtyinc.com/

I need to install something like this on my website and have no idea where to start.

Very, very basic implementation. The user interface is pretty different ugly, but there you go.

The magic is the following formula:

output = (input - 599) * 0.03

That's going to be the heart of your app, no matter how you build it.