Over the years, a lot of people have asked for calculator features like occasional extra principal reduction payments, tracking fees or late charges, summary of interest over a fiscal year. My pat response is “this kind of thing needs a spreadsheet or special-purpose software.”
Well, I’ve taken a little time to work up a basic amortization spreadsheet. It doesn’t have all the calculation options that the web calculator provides (it only calculates the payment, for example), but the amortization schedule it produces will allow one to track extra payments and fees, to include payments for insurance and taxes, and it provides a nice fiscal year summary of interest paid.
It took a few days of playing around with Excel to get it working mostly right, and it’s free for you to download and try, if you’re into that kind of thing. Maybe it will give you some ideas about how to build your own custom spreadsheet. But of course, use at your own risk! Please don’t base any high-finance decisions on the spreadsheet’s results until you’ve verified that it’s doing everything correctly. Like the web calculator, I consider this a planning tool only!
If you want to give it a shot, here’s a link to the spreadsheet. Enjoy!