I wrote the amortization calculator for my own use around 1986. I re-wrote it for use on the Web in 1994, running on a webserver in the FSU Meteorology Department. This site became its new home in 2008.
The calculator doesn’t just figure out the payment: it can fill in almost any of the other parameters for you, if you know what the rest of them are. It can even handle balloon payments, negative amortizations, and extra payments under certain circumstances. (See the FAQ link below for the specifics.)
Here are some local links regarding the calculator:
- The Amortization Calculator
- New! A Loan and Mortgage Excel Spreadsheet
- Blog posts on calculator modifications
- Frequently Asked Questions (FAQ)
- More Information
- The Mathematical Derivation (PDF)
- Formulae for payment moratorium and residual principal (PDF)
- More formulae for finding original payment parameters (PDF)
- Closed-form formulae for calculating per-payment interest and accumulated interest
If you’d like to make a request for a calculator feature, add a comment to the Feature Request page. (You’ll need to create an account.) Add a comment to the Questions page for general queries, and if you’ve think you’ve found bugs or mistakes, add a comment to the Bugs page.