I started this applet in the summer of 1995 as a way to learn Java programming. I was taking out my first mortgage at the time, so it seemed like a good way to combine my new-found curiosity about how mortgages worked, and as an alternative to writing a series of "Hello world!" programs.

Sharing an office with Ciarán Treanor certainly helped. He was quite a bit further along the Java programming curve than me, and had previous OO experience, so was able to help me get started.

I put it online fairly soon after writing the first version, and it had its fair share of visitors. Enough requests for the source code prompted me into believing that maybe it was more than a little bit useful. Since adding the graphing features it has become quite popular, and lots of people now use it on a regular basis.

It's also great to get feedback from people who were as confused as I was a few years ago about mortgages, but now, after having used the calculator, have a much better understanding of their own financial situation and have figured out how to save themselves (hundreds of) thousands of dollars over the terms of their mortgages.

In 2009, I created an Android version of the calculator, and in 2013, I did a complete re-write of the web code in Javascript. Java support was in decline and browsers weren't always loading the applet. So no more Java code on the web site now, however the original Java calculation code lives on in the Android app. In 2015, after many requests, I finally released an iOS version of the app.



Thanks go to:


Multiple language support thanks to:

More translations and fixes welcome - send me an email!


Comments, questions, suggestions, etc are always very welcome.

Please send your email to: karl@jeacle.ie