I don't know if this will be of any help... but I too needed link to a calculator from a site... but just a simple calc...

I gave up on widgets and coded stuff. Why? Because I'm totally retarded when it comes to such things... so...

I just did my simple calculator in Excel which allows you to embed it into a site.... took the embed code it provided, put it in a 'placeholder',
played around with sizes and such... and bam!... there it is!

Got the job done... Now I'm sure If you're any good at Excel, you can create a pretty sophisticated calculator.

HERE IT IS...